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	$135.88	8.855%	$147.9122	$147.91	$147.90	$147.90
Purchase #2	$58.52	3.862%	$60.78	$60.78	$60.80	$60.80
Purchase #3	$218.53	12.317%	$245.4463	$245.45	$245.45	$245.40
Purchase #4	$195.46	13.713%	$222.2634	$222.26	$222.25	$222.30
Purchase #5	$37.74	4.277%	$39.3541	$39.35	$39.35	$39.40
Purchase #6	$217.54	7.143%	$233.0789	$233.08	$233.10	$233.10
Purchase #7	$81.67	10.285%	$90.0698	$90.07	$90.05	$90.10
7 purchase totals =	$945.34		$1,038.9047	$1,038.90	$1,038.90	$1,039.00