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	$55.48	10.515%	$61.3137	$61.31	$61.30	$61.30
Purchase #2	$129.33	5.394%	$136.3061	$136.31	$136.30	$136.30
Purchase #3	$31.82	6.438%	$33.8686	$33.87	$33.85	$33.90
Purchase #4	$238.95	9.775%	$262.3074	$262.31	$262.30	$262.30
Purchase #5	$236.34	4.570%	$247.1407	$247.14	$247.15	$247.10
Purchase #6	$249.72	4.211%	$260.2357	$260.24	$260.25	$260.20
Purchase #7	$94.35	5.330%	$99.3789	$99.38	$99.40	$99.40
7 purchase totals =	$1,035.99		$1,100.5511	$1,100.56	$1,100.55	$1,100.50