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	$57.85	7.874%	$62.4051	$62.41	$62.40	$62.40
Purchase #2	$10.82	4.861%	$11.346	$11.35	$11.35	$11.30
Purchase #3	$90.72	9.623%	$99.45	$99.45	$99.45	$99.50
Purchase #4	$223.75	8.253%	$242.2161	$242.22	$242.20	$242.20
Purchase #5	$105.73	6.813%	$112.9334	$112.93	$112.95	$112.90
Purchase #6	$18.96	4.487%	$19.8107	$19.81	$19.80	$19.80
Purchase #7	$101.32	10.563%	$112.0224	$112.02	$112.00	$112.00
7 purchase totals =	$609.15		$660.1837	$660.19	$660.15	$660.10