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	$195.55	13.514%	$221.9766	$221.98	$222.00	$222.00
Purchase #2	$80.85	6.851%	$86.389	$86.39	$86.40	$86.40
Purchase #3	$209.71	11.556%	$233.9441	$233.94	$233.95	$233.90
Purchase #4	$159.31	7.429%	$171.1451	$171.15	$171.15	$171.10
Purchase #5	$230.70	5.787%	$244.0506	$244.05	$244.05	$244.10
Purchase #6	$93.99	6.216%	$99.8324	$99.83	$99.85	$99.80
Purchase #7	$42.38	7.874%	$45.717	$45.72	$45.70	$45.70
7 purchase totals =	$1,012.49		$1,103.0548	$1,103.06	$1,103.10	$1,103.00