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	$193.89	9.839%	$212.9668	$212.97	$212.95	$213.00
Purchase #2	$46.70	8.810%	$50.8143	$50.81	$50.80	$50.80
Purchase #3	$88.83	6.261%	$94.3916	$94.39	$94.40	$94.40
Purchase #4	$145.72	4.154%	$151.7732	$151.77	$151.75	$151.80
Purchase #5	$157.56	11.872%	$176.2655	$176.27	$176.25	$176.30
Purchase #6	$71.30	9.772%	$78.2674	$78.27	$78.25	$78.30
Purchase #7	$155.71	8.693%	$169.2459	$169.25	$169.25	$169.20
7 purchase totals =	$859.71		$933.7247	$933.73	$933.65	$933.80