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	$198.95	12.199%	$223.2199	$223.22	$223.20	$223.20
Purchase #2	$93.33	5.527%	$98.4883	$98.49	$98.50	$98.50
Purchase #3	$52.59	13.153%	$59.5072	$59.51	$59.50	$59.50
Purchase #4	$139.42	5.185%	$146.6489	$146.65	$146.65	$146.60
Purchase #5	$86.50	9.544%	$94.7556	$94.76	$94.75	$94.80
Purchase #6	$143.32	6.870%	$153.1661	$153.17	$153.15	$153.20
Purchase #7	$163.69	12.418%	$184.017	$184.02	$184.00	$184.00
7 purchase totals =	$877.80		$959.8030	$959.82	$959.75	$959.80