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	$67.58	7.698%	$72.7823	$72.78	$72.80	$72.80
Purchase #2	$52.57	4.794%	$55.0902	$55.09	$55.10	$55.10
Purchase #3	$63.61	6.767%	$67.9145	$67.91	$67.90	$67.90
Purchase #4	$30.72	9.371%	$33.5988	$33.60	$33.60	$33.60
Purchase #5	$48.89	11.614%	$54.5681	$54.57	$54.55	$54.60
Purchase #6	$18.67	11.372%	$20.7932	$20.79	$20.80	$20.80
Purchase #7	$34.59	6.623%	$36.8809	$36.88	$36.90	$36.90
7 purchase totals =	$316.63		$341.6280	$341.62	$341.65	$341.70