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	$83.28	8.578%	$90.4238	$90.42	$90.40	$90.40
Purchase #2	$117.81	5.377%	$124.1446	$124.14	$124.15	$124.10
Purchase #3	$118.44	12.392%	$133.1171	$133.12	$133.10	$133.10
Purchase #4	$201.39	6.815%	$215.1147	$215.11	$215.10	$215.10
Purchase #5	$48.78	9.587%	$53.4565	$53.46	$53.45	$53.50
Purchase #6	$207.89	7.502%	$223.4859	$223.49	$223.50	$223.50
Purchase #7	$182.91	5.247%	$192.5073	$192.51	$192.50	$192.50
7 purchase totals =	$960.50		$1,032.2499	$1,032.25	$1,032.20	$1,032.20