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	$164.64	5.751%	$174.1084	$174.11	$174.10	$174.10
Purchase #2	$175.27	5.198%	$184.3805	$184.38	$184.40	$184.40
Purchase #3	$125.69	3.319%	$129.8617	$129.86	$129.85	$129.90
Purchase #4	$136.57	4.762%	$143.0735	$143.07	$143.05	$143.10
Purchase #5	$73.83	9.236%	$80.6489	$80.65	$80.65	$80.60
Purchase #6	$89.41	12.580%	$100.6578	$100.66	$100.65	$100.70
Purchase #7	$79.61	12.432%	$89.5071	$89.51	$89.50	$89.50
7 purchase totals =	$845.02		$902.2379	$902.24	$902.20	$902.30