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	$149.57	7.253%	$160.4183	$160.42	$160.40	$160.40
Purchase #2	$95.84	7.364%	$102.8977	$102.90	$102.90	$102.90
Purchase #3	$58.96	4.809%	$61.7954	$61.80	$61.80	$61.80
Purchase #4	$137.34	10.200%	$151.3487	$151.35	$151.35	$151.30
Purchase #5	$19.51	13.675%	$22.178	$22.18	$22.20	$22.20
Purchase #6	$34.61	9.286%	$37.8239	$37.82	$37.80	$37.80
Purchase #7	$70.40	11.511%	$78.5037	$78.50	$78.50	$78.50
7 purchase totals =	$566.23		$614.9657	$614.97	$614.95	$614.90