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	$83.42	7.497%	$89.674	$89.67	$89.65	$89.70
Purchase #2	$174.29	4.760%	$182.5862	$182.59	$182.60	$182.60
Purchase #3	$162.50	6.406%	$172.9098	$172.91	$172.90	$172.90
Purchase #4	$44.63	7.538%	$47.9942	$47.99	$48.00	$48.00
Purchase #5	$246.89	9.313%	$269.8829	$269.88	$269.90	$269.90
Purchase #6	$124.35	8.278%	$134.6437	$134.64	$134.65	$134.60
Purchase #7	$135.60	10.513%	$149.8556	$149.86	$149.85	$149.90
7 purchase totals =	$971.68		$1,047.5464	$1,047.54	$1,047.55	$1,047.60