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	$93.83	7.485%	$100.8532	$100.85	$100.85	$100.90
Purchase #2	$21.71	6.711%	$23.167	$23.17	$23.15	$23.20
Purchase #3	$56.82	8.624%	$61.7202	$61.72	$61.70	$61.70
Purchase #4	$71.44	11.828%	$79.8899	$79.89	$79.90	$79.90
Purchase #5	$94.57	9.775%	$103.8142	$103.81	$103.80	$103.80
Purchase #6	$130.74	9.589%	$143.2767	$143.28	$143.30	$143.30
Purchase #7	$123.76	5.489%	$130.5532	$130.55	$130.55	$130.60
7 purchase totals =	$592.87		$643.2744	$643.27	$643.25	$643.40