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	$221.77	11.698%	$247.7127	$247.71	$247.70	$247.70
Purchase #2	$63.74	9.223%	$69.6187	$69.62	$69.60	$69.60
Purchase #3	$65.91	10.656%	$72.9334	$72.93	$72.95	$72.90
Purchase #4	$155.82	4.139%	$162.2694	$162.27	$162.25	$162.30
Purchase #5	$219.89	8.793%	$239.2249	$239.22	$239.20	$239.20
Purchase #6	$191.42	12.748%	$215.8222	$215.82	$215.80	$215.80
Purchase #7	$243.91	5.272%	$256.7689	$256.77	$256.75	$256.80
7 purchase totals =	$1,162.46		$1,264.3502	$1,264.34	$1,264.25	$1,264.30