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	$160.54	8.527%	$174.2292	$174.23	$174.25	$174.20
Purchase #2	$65.26	13.245%	$73.9037	$73.90	$73.90	$73.90
Purchase #3	$144.64	10.245%	$159.4584	$159.46	$159.45	$159.50
Purchase #4	$79.74	8.579%	$86.5809	$86.58	$86.60	$86.60
Purchase #5	$185.60	13.113%	$209.9377	$209.94	$209.95	$209.90
Purchase #6	$234.64	12.601%	$264.207	$264.21	$264.20	$264.20
Purchase #7	$199.46	11.302%	$222.003	$222.00	$222.00	$222.00
7 purchase totals =	$1,069.88		$1,190.3199	$1,190.32	$1,190.35	$1,190.30