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	$190.95	4.599%	$199.7318	$199.73	$199.75	$199.70
Purchase #2	$88.47	3.142%	$91.2497	$91.25	$91.25	$91.20
Purchase #3	$31.94	10.294%	$35.2279	$35.23	$35.25	$35.20
Purchase #4	$96.54	3.179%	$99.609	$99.61	$99.60	$99.60
Purchase #5	$95.54	4.801%	$100.1269	$100.13	$100.15	$100.10
Purchase #6	$130.67	7.197%	$140.0743	$140.07	$140.05	$140.10
Purchase #7	$35.71	8.142%	$38.6175	$38.62	$38.60	$38.60
7 purchase totals =	$669.82		$704.6371	$704.64	$704.65	$704.50