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	$175.58	4.162%	$182.8876	$182.89	$182.90	$182.90
Purchase #2	$27.91	12.868%	$31.5015	$31.50	$31.50	$31.50
Purchase #3	$10.43	9.615%	$11.4328	$11.43	$11.45	$11.40
Purchase #4	$195.84	7.113%	$209.7701	$209.77	$209.75	$209.80
Purchase #5	$190.62	4.332%	$198.8777	$198.88	$198.90	$198.90
Purchase #6	$66.87	7.362%	$71.793	$71.79	$71.80	$71.80
Purchase #7	$95.91	10.427%	$105.9105	$105.91	$105.90	$105.90
7 purchase totals =	$763.16		$812.1732	$812.17	$812.20	$812.20