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	$148.58	6.827%	$158.7236	$158.72	$158.70	$158.70
Purchase #2	$179.25	3.418%	$185.3768	$185.38	$185.40	$185.40
Purchase #3	$9.52	7.642%	$10.2475	$10.25	$10.25	$10.20
Purchase #4	$63.33	13.109%	$71.6319	$71.63	$71.65	$71.60
Purchase #5	$134.97	6.663%	$143.9631	$143.96	$143.95	$144.00
Purchase #6	$214.37	12.676%	$241.5435	$241.54	$241.55	$241.50
Purchase #7	$92.89	6.104%	$98.56	$98.56	$98.55	$98.60
7 purchase totals =	$842.91		$910.0464	$910.04	$910.05	$910.00