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	$225.83	4.143%	$235.1861	$235.19	$235.20	$235.20
Purchase #2	$12.69	6.465%	$13.5104	$13.51	$13.50	$13.50
Purchase #3	$128.65	11.343%	$143.2428	$143.24	$143.25	$143.20
Purchase #4	$162.86	5.434%	$171.7098	$171.71	$171.70	$171.70
Purchase #5	$163.89	13.862%	$186.6084	$186.61	$186.60	$186.60
Purchase #6	$26.38	3.791%	$27.3801	$27.38	$27.40	$27.40
Purchase #7	$172.33	11.308%	$191.8171	$191.82	$191.80	$191.80
7 purchase totals =	$892.63		$969.4547	$969.46	$969.45	$969.40