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	$34.32	9.282%	$37.5056	$37.51	$37.50	$37.50
Purchase #2	$22.61	12.840%	$25.5131	$25.51	$25.50	$25.50
Purchase #3	$50.91	11.270%	$56.6476	$56.65	$56.65	$56.60
Purchase #4	$65.33	8.764%	$71.0555	$71.06	$71.05	$71.10
Purchase #5	$35.83	7.456%	$38.5015	$38.50	$38.50	$38.50
Purchase #6	$197.49	5.441%	$208.2354	$208.24	$208.25	$208.20
Purchase #7	$43.78	7.619%	$47.1156	$47.12	$47.10	$47.10
7 purchase totals =	$450.27		$484.5743	$484.59	$484.55	$484.50