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	$57.69	11.832%	$64.5159	$64.52	$64.50	$64.50
Purchase #2	$22.74	13.117%	$25.7228	$25.72	$25.70	$25.70
Purchase #3	$231.93	11.678%	$259.0148	$259.01	$259.00	$259.00
Purchase #4	$139.63	4.619%	$146.0795	$146.08	$146.10	$146.10
Purchase #5	$182.37	7.352%	$195.7778	$195.78	$195.80	$195.80
Purchase #6	$156.86	3.745%	$162.7344	$162.73	$162.75	$162.70
Purchase #7	$102.33	8.541%	$111.07	$111.07	$111.05	$111.10
7 purchase totals =	$893.55		$964.9152	$964.91	$964.90	$964.90