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	$175.38	7.485%	$188.5072	$188.51	$188.50	$188.50
Purchase #2	$49.40	12.106%	$55.3804	$55.38	$55.40	$55.40
Purchase #3	$91.72	5.401%	$96.6738	$96.67	$96.65	$96.70
Purchase #4	$214.29	9.562%	$234.7804	$234.78	$234.80	$234.80
Purchase #5	$206.83	6.132%	$219.5128	$219.51	$219.50	$219.50
Purchase #6	$186.89	7.843%	$201.5478	$201.55	$201.55	$201.50
Purchase #7	$28.89	11.860%	$32.3164	$32.32	$32.30	$32.30
7 purchase totals =	$953.40		$1,028.7188	$1,028.72	$1,028.70	$1,028.70