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	$109.66	4.813%	$114.9379	$114.94	$114.95	$114.90
Purchase #2	$227.89	4.363%	$237.8328	$237.83	$237.85	$237.80
Purchase #3	$70.79	10.625%	$78.3114	$78.31	$78.30	$78.30
Purchase #4	$109.35	13.137%	$123.7153	$123.72	$123.70	$123.70
Purchase #5	$141.58	6.228%	$150.3976	$150.40	$150.40	$150.40
Purchase #6	$136.77	6.452%	$145.5944	$145.59	$145.60	$145.60
Purchase #7	$45.81	10.304%	$50.5303	$50.53	$50.55	$50.50
7 purchase totals =	$841.85		$901.3197	$901.32	$901.35	$901.20