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	$167.38	12.201%	$187.802	$187.80	$187.80	$187.80
Purchase #2	$166.67	7.511%	$179.1886	$179.19	$179.20	$179.20
Purchase #3	$53.52	7.468%	$57.5169	$57.52	$57.50	$57.50
Purchase #4	$56.79	8.745%	$61.7563	$61.76	$61.75	$61.80
Purchase #5	$89.53	7.477%	$96.2242	$96.22	$96.20	$96.20
Purchase #6	$200.92	12.290%	$225.6131	$225.61	$225.60	$225.60
Purchase #7	$78.51	4.604%	$82.1246	$82.12	$82.10	$82.10
7 purchase totals =	$813.32		$890.2257	$890.22	$890.15	$890.20