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	$97.62	11.745%	$109.0855	$109.09	$109.10	$109.10
Purchase #2	$229.62	11.195%	$255.326	$255.33	$255.35	$255.30
Purchase #3	$15.81	9.474%	$17.3078	$17.31	$17.30	$17.30
Purchase #4	$160.46	13.622%	$182.3179	$182.32	$182.30	$182.30
Purchase #5	$146.92	12.742%	$165.6405	$165.64	$165.65	$165.60
Purchase #6	$84.51	13.281%	$95.7338	$95.73	$95.75	$95.70
Purchase #7	$99.88	4.256%	$104.1309	$104.13	$104.15	$104.10
7 purchase totals =	$834.82		$929.5424	$929.55	$929.60	$929.40