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	$175.94	12.844%	$198.5377	$198.54	$198.55	$198.50
Purchase #2	$220.71	9.141%	$240.8851	$240.89	$240.90	$240.90
Purchase #3	$48.43	12.767%	$54.6131	$54.61	$54.60	$54.60
Purchase #4	$182.66	5.142%	$192.0524	$192.05	$192.05	$192.10
Purchase #5	$67.69	9.139%	$73.8762	$73.88	$73.90	$73.90
Purchase #6	$204.31	12.356%	$229.5545	$229.55	$229.55	$229.60
Purchase #7	$150.86	6.126%	$160.1017	$160.10	$160.10	$160.10
7 purchase totals =	$1,050.60		$1,149.6207	$1,149.62	$1,149.65	$1,149.70