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	$119.78	4.297%	$124.9269	$124.93	$124.95	$124.90
Purchase #2	$218.84	10.589%	$242.013	$242.01	$242.00	$242.00
Purchase #3	$141.47	3.489%	$146.4059	$146.41	$146.40	$146.40
Purchase #4	$59.69	4.768%	$62.536	$62.54	$62.55	$62.50
Purchase #5	$185.84	3.504%	$192.3518	$192.35	$192.35	$192.40
Purchase #6	$117.78	8.379%	$127.6488	$127.65	$127.65	$127.60
Purchase #7	$91.54	12.662%	$103.1308	$103.13	$103.15	$103.10
7 purchase totals =	$934.94		$999.0132	$999.02	$999.05	$998.90