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	$110.46	8.299%	$119.6271	$119.63	$119.65	$119.60
Purchase #2	$176.70	11.373%	$196.7961	$196.80	$196.80	$196.80
Purchase #3	$213.94	12.627%	$240.9542	$240.95	$240.95	$241.00
Purchase #4	$139.56	6.141%	$148.1304	$148.13	$148.15	$148.10
Purchase #5	$188.42	8.582%	$204.5902	$204.59	$204.60	$204.60
Purchase #6	$100.60	10.472%	$111.1348	$111.13	$111.15	$111.10
Purchase #7	$79.71	4.683%	$83.4428	$83.44	$83.45	$83.40
7 purchase totals =	$1,009.39		$1,104.6756	$1,104.67	$1,104.75	$1,104.60