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	$89.31	3.590%	$92.5162	$92.52	$92.50	$92.50
Purchase #2	$165.27	3.821%	$171.585	$171.59	$171.60	$171.60
Purchase #3	$27.89	11.414%	$31.0734	$31.07	$31.05	$31.10
Purchase #4	$50.57	13.732%	$57.5143	$57.51	$57.50	$57.50
Purchase #5	$119.47	9.621%	$130.9642	$130.96	$130.95	$131.00
Purchase #6	$230.62	9.827%	$253.283	$253.28	$253.30	$253.30
Purchase #7	$209.89	3.454%	$217.1396	$217.14	$217.15	$217.10
7 purchase totals =	$893.02		$954.0757	$954.07	$954.05	$954.10