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	$212.48	6.238%	$225.7345	$225.73	$225.75	$225.70
Purchase #2	$51.77	7.614%	$55.7118	$55.71	$55.70	$55.70
Purchase #3	$224.87	7.433%	$241.5846	$241.58	$241.60	$241.60
Purchase #4	$43.82	9.284%	$47.8882	$47.89	$47.90	$47.90
Purchase #5	$201.97	4.415%	$210.887	$210.89	$210.90	$210.90
Purchase #6	$146.38	13.839%	$166.6375	$166.64	$166.65	$166.60
Purchase #7	$18.69	11.561%	$20.8508	$20.85	$20.85	$20.90
7 purchase totals =	$899.98		$969.2944	$969.29	$969.35	$969.30