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	$91.49	3.719%	$94.8925	$94.89	$94.90	$94.90
Purchase #2	$124.33	10.313%	$137.1522	$137.15	$137.15	$137.20
Purchase #3	$188.29	4.582%	$196.9174	$196.92	$196.90	$196.90
Purchase #4	$230.34	12.222%	$258.4922	$258.49	$258.50	$258.50
Purchase #5	$58.72	7.113%	$62.8968	$62.90	$62.90	$62.90
Purchase #6	$144.28	4.259%	$150.4249	$150.42	$150.40	$150.40
Purchase #7	$198.73	4.565%	$207.802	$207.80	$207.80	$207.80
7 purchase totals =	$1,036.18		$1,108.5780	$1,108.57	$1,108.55	$1,108.60