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	$212.93	5.128%	$223.8491	$223.85	$223.85	$223.80
Purchase #2	$52.75	10.146%	$58.102	$58.10	$58.10	$58.10
Purchase #3	$154.83	7.498%	$166.4392	$166.44	$166.45	$166.40
Purchase #4	$131.80	8.306%	$142.7473	$142.75	$142.75	$142.70
Purchase #5	$215.44	12.797%	$243.0099	$243.01	$243.00	$243.00
Purchase #6	$18.78	9.736%	$20.6084	$20.61	$20.60	$20.60
Purchase #7	$173.44	13.503%	$196.8596	$196.86	$196.85	$196.90
7 purchase totals =	$959.97		$1,051.6155	$1,051.62	$1,051.60	$1,051.50