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	$169.50	7.321%	$181.9091	$181.91	$181.90	$181.90
Purchase #2	$179.62	6.506%	$191.3061	$191.31	$191.30	$191.30
Purchase #3	$239.67	10.140%	$263.9725	$263.97	$263.95	$264.00
Purchase #4	$52.25	6.543%	$55.6687	$55.67	$55.65	$55.70
Purchase #5	$148.54	13.567%	$168.6924	$168.69	$168.70	$168.70
Purchase #6	$117.53	4.836%	$123.2138	$123.21	$123.20	$123.20
Purchase #7	$165.37	8.626%	$179.6348	$179.63	$179.65	$179.60
7 purchase totals =	$1,072.48		$1,164.3974	$1,164.39	$1,164.35	$1,164.40