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	$114.53	13.702%	$130.2229	$130.22	$130.20	$130.20
Purchase #2	$173.63	6.871%	$185.5601	$185.56	$185.55	$185.60
Purchase #3	$224.77	11.640%	$250.9332	$250.93	$250.95	$250.90
Purchase #4	$113.62	8.816%	$123.6367	$123.64	$123.65	$123.60
Purchase #5	$78.97	12.225%	$88.6241	$88.62	$88.60	$88.60
Purchase #6	$52.61	10.732%	$58.2561	$58.26	$58.25	$58.30
Purchase #7	$202.42	6.862%	$216.3101	$216.31	$216.30	$216.30
7 purchase totals =	$960.55		$1,053.5432	$1,053.54	$1,053.50	$1,053.50