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	$117.42	11.464%	$130.881	$130.88	$130.90	$130.90
Purchase #2	$171.91	3.756%	$178.3669	$178.37	$178.35	$178.40
Purchase #3	$234.66	10.504%	$259.3087	$259.31	$259.30	$259.30
Purchase #4	$82.95	6.814%	$88.6022	$88.60	$88.60	$88.60
Purchase #5	$135.88	10.638%	$150.3349	$150.33	$150.35	$150.30
Purchase #6	$59.87	4.811%	$62.7503	$62.75	$62.75	$62.80
Purchase #7	$170.39	7.356%	$182.9239	$182.92	$182.90	$182.90
7 purchase totals =	$973.08		$1,053.1679	$1,053.16	$1,053.15	$1,053.20