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	$134.43	6.469%	$143.1263	$143.13	$143.15	$143.10
Purchase #2	$132.63	4.121%	$138.0957	$138.10	$138.10	$138.10
Purchase #3	$236.34	4.645%	$247.318	$247.32	$247.30	$247.30
Purchase #4	$139.40	10.820%	$154.4831	$154.48	$154.50	$154.50
Purchase #5	$53.59	11.363%	$59.6794	$59.68	$59.70	$59.70
Purchase #6	$181.80	10.298%	$200.5218	$200.52	$200.50	$200.50
Purchase #7	$89.40	11.374%	$99.5684	$99.57	$99.55	$99.60
7 purchase totals =	$967.59		$1,042.7927	$1,042.80	$1,042.80	$1,042.80