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	$45.61	11.667%	$50.9313	$50.93	$50.95	$50.90
Purchase #2	$60.46	8.547%	$65.6275	$65.63	$65.65	$65.60
Purchase #3	$48.86	4.276%	$50.9493	$50.95	$50.95	$50.90
Purchase #4	$29.96	11.297%	$33.3446	$33.34	$33.35	$33.30
Purchase #5	$124.85	11.141%	$138.7595	$138.76	$138.75	$138.80
Purchase #6	$234.68	13.724%	$266.8875	$266.89	$266.90	$266.90
Purchase #7	$142.65	6.243%	$151.5556	$151.56	$151.55	$151.60
7 purchase totals =	$687.07		$758.0553	$758.06	$758.10	$758.00