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	$145.74	6.303%	$154.926	$154.93	$154.95	$154.90
Purchase #2	$42.94	10.268%	$47.3491	$47.35	$47.35	$47.30
Purchase #3	$168.85	9.241%	$184.4534	$184.45	$184.45	$184.50
Purchase #4	$59.50	3.306%	$61.4671	$61.47	$61.45	$61.50
Purchase #5	$128.59	3.667%	$133.3054	$133.31	$133.30	$133.30
Purchase #6	$65.68	11.845%	$73.4598	$73.46	$73.45	$73.50
Purchase #7	$36.78	9.283%	$40.1943	$40.19	$40.20	$40.20
7 purchase totals =	$648.08		$695.1551	$695.16	$695.15	$695.20