Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.61	13.663%	$190.5106	$190.51	$190.50	$190.50
Purchase #2	$146.62	12.834%	$165.4372	$165.44	$165.45	$165.40
Purchase #3	$234.89	8.523%	$254.9097	$254.91	$254.90	$254.90
Purchase #4	$170.97	10.273%	$188.5337	$188.53	$188.55	$188.50
Purchase #5	$162.38	7.685%	$174.8589	$174.86	$174.85	$174.90
Purchase #6	$224.54	4.237%	$234.0538	$234.05	$234.05	$234.10
Purchase #7	$169.54	10.851%	$187.9368	$187.94	$187.95	$187.90
7 purchase totals =	$1,276.55		$1,396.2407	$1,396.24	$1,396.25	$1,396.20