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	$75.92	8.463%	$82.3451	$82.35	$82.35	$82.30
Purchase #2	$58.37	5.266%	$61.4438	$61.44	$61.45	$61.40
Purchase #3	$181.90	7.201%	$194.9986	$195.00	$195.00	$195.00
Purchase #4	$235.70	8.340%	$255.3574	$255.36	$255.35	$255.40
Purchase #5	$118.58	4.490%	$123.9042	$123.90	$123.90	$123.90
Purchase #6	$216.94	13.855%	$246.997	$247.00	$247.00	$247.00
Purchase #7	$98.76	6.573%	$105.2515	$105.25	$105.25	$105.30
7 purchase totals =	$986.17		$1,070.2976	$1,070.30	$1,070.30	$1,070.30