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	$215.42	10.141%	$237.2657	$237.27	$237.25	$237.30
Purchase #2	$109.38	13.317%	$123.9461	$123.95	$123.95	$123.90
Purchase #3	$230.79	13.788%	$262.6113	$262.61	$262.60	$262.60
Purchase #4	$238.32	8.690%	$259.03	$259.03	$259.05	$259.00
Purchase #5	$188.85	3.144%	$194.7874	$194.79	$194.80	$194.80
Purchase #6	$146.82	12.874%	$165.7216	$165.72	$165.70	$165.70
Purchase #7	$83.60	7.119%	$89.5515	$89.55	$89.55	$89.60
7 purchase totals =	$1,213.18		$1,332.9136	$1,332.92	$1,332.90	$1,332.90