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	$85.81	12.344%	$96.4024	$96.40	$96.40	$96.40
Purchase #2	$112.53	5.309%	$118.5042	$118.50	$118.50	$118.50
Purchase #3	$55.37	8.116%	$59.8638	$59.86	$59.85	$59.90
Purchase #4	$51.54	7.109%	$55.204	$55.20	$55.20	$55.20
Purchase #5	$239.68	6.306%	$254.7942	$254.79	$254.80	$254.80
Purchase #6	$188.89	6.358%	$200.8996	$200.90	$200.90	$200.90
Purchase #7	$173.79	8.746%	$188.9897	$188.99	$189.00	$189.00
7 purchase totals =	$907.61		$974.6579	$974.64	$974.65	$974.70