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	$147.91	9.707%	$162.2676	$162.27	$162.25	$162.30
Purchase #2	$72.32	12.226%	$81.1618	$81.16	$81.15	$81.20
Purchase #3	$187.57	11.699%	$209.5138	$209.51	$209.50	$209.50
Purchase #4	$162.82	13.853%	$185.3755	$185.38	$185.40	$185.40
Purchase #5	$36.47	7.357%	$39.1531	$39.15	$39.15	$39.20
Purchase #6	$170.73	10.545%	$188.7335	$188.73	$188.75	$188.70
Purchase #7	$218.78	4.493%	$228.6098	$228.61	$228.60	$228.60
7 purchase totals =	$996.60		$1,094.8151	$1,094.81	$1,094.80	$1,094.90