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	$55.51	7.611%	$59.7349	$59.73	$59.75	$59.70
Purchase #2	$229.52	8.342%	$248.6666	$248.67	$248.65	$248.70
Purchase #3	$52.63	6.840%	$56.2299	$56.23	$56.25	$56.20
Purchase #4	$148.42	11.798%	$165.9306	$165.93	$165.95	$165.90
Purchase #5	$185.86	5.395%	$195.8871	$195.89	$195.90	$195.90
Purchase #6	$205.66	6.599%	$219.2315	$219.23	$219.25	$219.20
Purchase #7	$185.42	10.759%	$205.3693	$205.37	$205.35	$205.40
7 purchase totals =	$1,063.02		$1,151.0499	$1,151.05	$1,151.10	$1,151.00