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	$195.26	13.680%	$221.9716	$221.97	$221.95	$222.00
Purchase #2	$125.75	13.255%	$142.4182	$142.42	$142.40	$142.40
Purchase #3	$88.57	11.822%	$99.0407	$99.04	$99.05	$99.00
Purchase #4	$187.29	11.507%	$208.8415	$208.84	$208.85	$208.80
Purchase #5	$56.34	9.241%	$61.5464	$61.55	$61.55	$61.50
Purchase #6	$223.86	8.685%	$243.3022	$243.30	$243.30	$243.30
Purchase #7	$181.97	11.798%	$203.4388	$203.44	$203.45	$203.40
7 purchase totals =	$1,059.04		$1,180.5594	$1,180.56	$1,180.55	$1,180.40