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	$91.65	6.632%	$97.7282	$97.73	$97.75	$97.70
Purchase #2	$178.28	3.591%	$184.682	$184.68	$184.70	$184.70
Purchase #3	$45.55	13.487%	$51.6933	$51.69	$51.70	$51.70
Purchase #4	$78.82	5.167%	$82.8926	$82.89	$82.90	$82.90
Purchase #5	$223.82	12.412%	$251.6005	$251.60	$251.60	$251.60
Purchase #6	$173.76	13.180%	$196.6616	$196.66	$196.65	$196.70
Purchase #7	$36.82	6.397%	$39.1754	$39.18	$39.20	$39.20
7 purchase totals =	$828.70		$904.4336	$904.43	$904.50	$904.50