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	$152.96	8.819%	$166.4495	$166.45	$166.45	$166.40
Purchase #2	$190.59	13.139%	$215.6316	$215.63	$215.65	$215.60
Purchase #3	$153.59	3.185%	$158.4818	$158.48	$158.50	$158.50
Purchase #4	$215.86	10.629%	$238.8038	$238.80	$238.80	$238.80
Purchase #5	$214.90	4.604%	$224.794	$224.79	$224.80	$224.80
Purchase #6	$76.86	11.473%	$85.6781	$85.68	$85.70	$85.70
Purchase #7	$189.33	12.743%	$213.4563	$213.46	$213.45	$213.50
7 purchase totals =	$1,194.09		$1,303.2951	$1,303.29	$1,303.35	$1,303.30