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	$193.38	8.115%	$209.0728	$209.07	$209.05	$209.10
Purchase #2	$117.89	7.831%	$127.122	$127.12	$127.10	$127.10
Purchase #3	$42.82	8.234%	$46.3458	$46.35	$46.35	$46.30
Purchase #4	$229.30	11.755%	$256.2542	$256.25	$256.25	$256.30
Purchase #5	$188.76	10.847%	$209.2348	$209.23	$209.25	$209.20
Purchase #6	$18.67	12.566%	$21.0161	$21.02	$21.00	$21.00
Purchase #7	$108.94	13.801%	$123.9748	$123.97	$123.95	$124.00
7 purchase totals =	$899.76		$993.0205	$993.01	$992.95	$993.00