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	$82.66	8.690%	$89.8432	$89.84	$89.85	$89.80
Purchase #2	$82.35	3.367%	$85.1227	$85.12	$85.10	$85.10
Purchase #3	$60.94	5.139%	$64.0717	$64.07	$64.05	$64.10
Purchase #4	$244.87	8.776%	$266.3598	$266.36	$266.35	$266.40
Purchase #5	$56.70	7.179%	$60.7705	$60.77	$60.75	$60.80
Purchase #6	$199.96	12.265%	$224.4851	$224.49	$224.50	$224.50
Purchase #7	$141.54	6.304%	$150.4627	$150.46	$150.45	$150.50
7 purchase totals =	$869.02		$941.1157	$941.11	$941.05	$941.20