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	$61.67	6.385%	$65.6076	$65.61	$65.60	$65.60
Purchase #2	$119.81	9.282%	$130.9308	$130.93	$130.95	$130.90
Purchase #3	$99.67	3.851%	$103.5083	$103.51	$103.50	$103.50
Purchase #4	$135.82	11.687%	$151.6933	$151.69	$151.70	$151.70
Purchase #5	$186.41	6.785%	$199.0579	$199.06	$199.05	$199.10
Purchase #6	$63.97	12.217%	$71.7852	$71.79	$71.80	$71.80
Purchase #7	$27.62	4.799%	$28.9455	$28.95	$28.95	$28.90
7 purchase totals =	$694.97		$751.5286	$751.54	$751.55	$751.50