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	$65.61	7.117%	$70.2795	$70.28	$70.30	$70.30
Purchase #2	$162.38	7.468%	$174.5065	$174.51	$174.50	$174.50
Purchase #3	$140.97	8.367%	$152.765	$152.77	$152.75	$152.80
Purchase #4	$230.69	7.738%	$248.5408	$248.54	$248.55	$248.50
Purchase #5	$123.78	7.630%	$133.2244	$133.22	$133.20	$133.20
Purchase #6	$86.68	10.717%	$95.9695	$95.97	$95.95	$96.00
Purchase #7	$181.82	7.871%	$196.1311	$196.13	$196.15	$196.10
7 purchase totals =	$991.93		$1,071.4168	$1,071.42	$1,071.40	$1,071.40