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	$105.51	5.809%	$111.6391	$111.64	$111.65	$111.60
Purchase #2	$210.51	10.249%	$232.0852	$232.09	$232.10	$232.10
Purchase #3	$139.74	7.601%	$150.3616	$150.36	$150.35	$150.40
Purchase #4	$122.63	13.713%	$139.4463	$139.45	$139.45	$139.40
Purchase #5	$125.53	11.642%	$140.1442	$140.14	$140.15	$140.10
Purchase #6	$133.40	12.834%	$150.5206	$150.52	$150.50	$150.50
Purchase #7	$16.97	9.782%	$18.63	$18.63	$18.65	$18.60
7 purchase totals =	$854.29		$942.8270	$942.83	$942.85	$942.70