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	$226.88	4.280%	$236.5905	$236.59	$236.60	$236.60
Purchase #2	$84.32	6.839%	$90.0866	$90.09	$90.10	$90.10
Purchase #3	$188.97	8.361%	$204.7698	$204.77	$204.75	$204.80
Purchase #4	$201.76	10.219%	$222.3779	$222.38	$222.40	$222.40
Purchase #5	$20.35	10.563%	$22.4996	$22.50	$22.50	$22.50
Purchase #6	$84.83	10.481%	$93.721	$93.72	$93.70	$93.70
Purchase #7	$173.32	10.642%	$191.7647	$191.76	$191.75	$191.80
7 purchase totals =	$980.43		$1,061.8101	$1,061.81	$1,061.80	$1,061.90