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	$235.39	11.464%	$262.3751	$262.38	$262.40	$262.40
Purchase #2	$41.30	13.248%	$46.7714	$46.77	$46.75	$46.80
Purchase #3	$135.32	12.691%	$152.4935	$152.49	$152.50	$152.50
Purchase #4	$247.68	3.102%	$255.363	$255.36	$255.35	$255.40
Purchase #5	$142.79	9.599%	$156.4964	$156.50	$156.50	$156.50
Purchase #6	$214.81	13.785%	$244.4216	$244.42	$244.40	$244.40
Purchase #7	$30.63	9.727%	$33.6094	$33.61	$33.60	$33.60
7 purchase totals =	$1,047.92		$1,151.5304	$1,151.53	$1,151.50	$1,151.60