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	$207.66	7.439%	$223.1078	$223.11	$223.10	$223.10
Purchase #2	$243.61	10.433%	$269.0258	$269.03	$269.05	$269.00
Purchase #3	$229.37	6.728%	$244.802	$244.80	$244.80	$244.80
Purchase #4	$155.70	8.350%	$168.701	$168.70	$168.70	$168.70
Purchase #5	$35.39	6.219%	$37.5909	$37.59	$37.60	$37.60
Purchase #6	$35.61	12.360%	$40.0114	$40.01	$40.00	$40.00
Purchase #7	$123.80	11.185%	$137.647	$137.65	$137.65	$137.60
7 purchase totals =	$1,031.14		$1,120.8859	$1,120.89	$1,120.90	$1,120.80