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	$55.74	7.513%	$59.9277	$59.93	$59.95	$59.90
Purchase #2	$135.75	10.126%	$149.496	$149.50	$149.50	$149.50
Purchase #3	$110.42	3.587%	$114.3808	$114.38	$114.40	$114.40
Purchase #4	$20.80	8.548%	$22.578	$22.58	$22.60	$22.60
Purchase #5	$250.41	5.560%	$264.3328	$264.33	$264.35	$264.30
Purchase #6	$51.71	7.760%	$55.7227	$55.72	$55.70	$55.70
Purchase #7	$39.42	3.871%	$40.9459	$40.95	$40.95	$40.90
7 purchase totals =	$664.25		$707.3839	$707.39	$707.45	$707.30