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	$173.66	5.807%	$183.7444	$183.74	$183.75	$183.70
Purchase #2	$131.90	11.726%	$147.3666	$147.37	$147.35	$147.40
Purchase #3	$100.38	6.483%	$106.8876	$106.89	$106.90	$106.90
Purchase #4	$121.63	8.454%	$131.9126	$131.91	$131.90	$131.90
Purchase #5	$230.40	3.707%	$238.9409	$238.94	$238.95	$238.90
Purchase #6	$55.42	3.293%	$57.245	$57.25	$57.25	$57.20
Purchase #7	$189.95	13.209%	$215.0405	$215.04	$215.05	$215.00
7 purchase totals =	$1,003.34		$1,081.1376	$1,081.14	$1,081.15	$1,081.00