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	$155.43	12.629%	$175.0593	$175.06	$175.05	$175.10
Purchase #2	$175.64	13.625%	$199.571	$199.57	$199.55	$199.60
Purchase #3	$72.27	12.520%	$81.3182	$81.32	$81.30	$81.30
Purchase #4	$132.86	7.518%	$142.8484	$142.85	$142.85	$142.80
Purchase #5	$203.28	7.808%	$219.1521	$219.15	$219.15	$219.20
Purchase #6	$90.44	10.279%	$99.7363	$99.74	$99.75	$99.70
Purchase #7	$104.32	9.207%	$113.9247	$113.92	$113.90	$113.90
7 purchase totals =	$934.24		$1,031.6100	$1,031.61	$1,031.55	$1,031.60