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	$245.45	7.267%	$263.2869	$263.29	$263.30	$263.30
Purchase #2	$244.79	4.587%	$256.0185	$256.02	$256.00	$256.00
Purchase #3	$99.42	3.393%	$102.7933	$102.79	$102.80	$102.80
Purchase #4	$215.76	13.673%	$245.2609	$245.26	$245.25	$245.30
Purchase #5	$210.34	3.516%	$217.7356	$217.74	$217.75	$217.70
Purchase #6	$63.31	4.531%	$66.1786	$66.18	$66.20	$66.20
Purchase #7	$73.76	11.621%	$82.3316	$82.33	$82.35	$82.30
7 purchase totals =	$1,152.83		$1,233.6054	$1,233.61	$1,233.65	$1,233.60