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	$105.85	6.624%	$112.8615	$112.86	$112.85	$112.90
Purchase #2	$67.46	12.872%	$76.1435	$76.14	$76.15	$76.10
Purchase #3	$14.55	8.554%	$15.7946	$15.79	$15.80	$15.80
Purchase #4	$121.78	7.373%	$130.7588	$130.76	$130.75	$130.80
Purchase #5	$196.31	13.261%	$222.3427	$222.34	$222.35	$222.30
Purchase #6	$233.57	4.435%	$243.9288	$243.93	$243.95	$243.90
Purchase #7	$162.92	12.181%	$182.7653	$182.77	$182.75	$182.80
7 purchase totals =	$902.44		$984.5952	$984.59	$984.60	$984.60