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	$196.72	4.213%	$205.0078	$205.01	$205.00	$205.00
Purchase #2	$247.28	12.573%	$278.3705	$278.37	$278.35	$278.40
Purchase #3	$217.51	13.334%	$246.5128	$246.51	$246.50	$246.50
Purchase #4	$156.59	5.133%	$164.6278	$164.63	$164.65	$164.60
Purchase #5	$91.62	8.155%	$99.0916	$99.09	$99.10	$99.10
Purchase #6	$89.53	8.423%	$97.0711	$97.07	$97.05	$97.10
Purchase #7	$57.95	7.140%	$62.0876	$62.09	$62.10	$62.10
7 purchase totals =	$1,057.20		$1,152.7692	$1,152.77	$1,152.75	$1,152.80