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	$196.77	12.798%	$221.9526	$221.95	$221.95	$222.00
Purchase #2	$32.27	9.782%	$35.4267	$35.43	$35.45	$35.40
Purchase #3	$127.39	8.223%	$137.8653	$137.87	$137.85	$137.90
Purchase #4	$199.72	5.545%	$210.7945	$210.79	$210.80	$210.80
Purchase #5	$173.84	6.362%	$184.8997	$184.90	$184.90	$184.90
Purchase #6	$13.57	9.760%	$14.8944	$14.89	$14.90	$14.90
Purchase #7	$60.78	8.524%	$65.9609	$65.96	$65.95	$66.00
7 purchase totals =	$804.34		$871.7941	$871.79	$871.80	$871.90