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	$43.72	5.595%	$46.1661	$46.17	$46.15	$46.20
Purchase #2	$86.82	13.772%	$98.7769	$98.78	$98.80	$98.80
Purchase #3	$41.26	6.414%	$43.9064	$43.91	$43.90	$43.90
Purchase #4	$87.26	7.162%	$93.5096	$93.51	$93.50	$93.50
Purchase #5	$77.41	6.363%	$82.3356	$82.34	$82.35	$82.30
Purchase #6	$146.58	4.331%	$152.9284	$152.93	$152.95	$152.90
Purchase #7	$127.96	4.638%	$133.8948	$133.89	$133.90	$133.90
7 purchase totals =	$611.01		$651.5178	$651.53	$651.55	$651.50