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	$60.73	8.231%	$65.7287	$65.73	$65.75	$65.70
Purchase #2	$224.31	6.338%	$238.5268	$238.53	$238.55	$238.50
Purchase #3	$17.28	6.327%	$18.3733	$18.37	$18.35	$18.40
Purchase #4	$73.62	10.501%	$81.3508	$81.35	$81.35	$81.40
Purchase #5	$36.80	13.791%	$41.8751	$41.88	$41.90	$41.90
Purchase #6	$228.37	12.299%	$256.4572	$256.46	$256.45	$256.50
Purchase #7	$70.40	11.393%	$78.4207	$78.42	$78.40	$78.40
7 purchase totals =	$711.51		$780.7326	$780.74	$780.75	$780.80