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	$133.93	7.413%	$143.8582	$143.86	$143.85	$143.90
Purchase #2	$8.89	8.374%	$9.6344	$9.63	$9.65	$9.60
Purchase #3	$94.86	11.524%	$105.7917	$105.79	$105.80	$105.80
Purchase #4	$111.28	11.194%	$123.7367	$123.74	$123.75	$123.70
Purchase #5	$10.58	7.617%	$11.3859	$11.39	$11.40	$11.40
Purchase #6	$98.47	10.663%	$108.9699	$108.97	$108.95	$109.00
Purchase #7	$143.30	5.479%	$151.1514	$151.15	$151.15	$151.20
7 purchase totals =	$601.31		$654.5282	$654.53	$654.55	$654.60