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	$137.74	11.379%	$153.4134	$153.41	$153.40	$153.40
Purchase #2	$100.62	9.547%	$110.2262	$110.23	$110.25	$110.20
Purchase #3	$96.89	7.444%	$104.1025	$104.10	$104.10	$104.10
Purchase #4	$221.78	9.697%	$243.286	$243.29	$243.30	$243.30
Purchase #5	$180.28	6.192%	$191.4429	$191.44	$191.45	$191.40
Purchase #6	$149.93	9.861%	$164.7146	$164.71	$164.70	$164.70
Purchase #7	$151.48	3.262%	$156.4213	$156.42	$156.40	$156.40
7 purchase totals =	$1,038.72		$1,123.6069	$1,123.60	$1,123.60	$1,123.50