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	$171.36	10.384%	$189.154	$189.15	$189.15	$189.20
Purchase #2	$231.81	10.741%	$256.7087	$256.71	$256.70	$256.70
Purchase #3	$161.83	13.298%	$183.3502	$183.35	$183.35	$183.40
Purchase #4	$48.67	13.215%	$55.1017	$55.10	$55.10	$55.10
Purchase #5	$154.87	9.502%	$169.5857	$169.59	$169.60	$169.60
Purchase #6	$180.34	4.743%	$188.8935	$188.89	$188.90	$188.90
Purchase #7	$39.60	9.854%	$43.5022	$43.50	$43.50	$43.50
7 purchase totals =	$988.48		$1,086.2960	$1,086.29	$1,086.30	$1,086.40