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	$97.93	8.551%	$106.304	$106.30	$106.30	$106.30
Purchase #2	$134.34	10.801%	$148.8501	$148.85	$148.85	$148.90
Purchase #3	$199.93	11.392%	$222.706	$222.71	$222.70	$222.70
Purchase #4	$224.59	6.805%	$239.8733	$239.87	$239.85	$239.90
Purchase #5	$119.57	12.398%	$134.3943	$134.39	$134.40	$134.40
Purchase #6	$69.71	3.141%	$71.8996	$71.90	$71.90	$71.90
Purchase #7	$109.54	11.635%	$122.285	$122.29	$122.30	$122.30
7 purchase totals =	$955.61		$1,046.3123	$1,046.31	$1,046.30	$1,046.40