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	$119.40	7.595%	$128.4684	$128.47	$128.45	$128.50
Purchase #2	$213.34	4.371%	$222.6651	$222.67	$222.65	$222.70
Purchase #3	$221.78	3.478%	$229.4935	$229.49	$229.50	$229.50
Purchase #4	$246.54	6.115%	$261.6159	$261.62	$261.60	$261.60
Purchase #5	$166.32	7.569%	$178.9088	$178.91	$178.90	$178.90
Purchase #6	$208.63	6.546%	$222.2869	$222.29	$222.30	$222.30
Purchase #7	$73.95	7.294%	$79.3439	$79.34	$79.35	$79.30
7 purchase totals =	$1,249.96		$1,322.7825	$1,322.79	$1,322.75	$1,322.80