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	$146.62	5.823%	$155.1577	$155.16	$155.15	$155.20
Purchase #2	$249.26	4.144%	$259.5893	$259.59	$259.60	$259.60
Purchase #3	$80.80	3.436%	$83.5763	$83.58	$83.60	$83.60
Purchase #4	$105.41	10.303%	$116.2704	$116.27	$116.25	$116.30
Purchase #5	$95.44	3.132%	$98.4292	$98.43	$98.45	$98.40
Purchase #6	$92.73	13.369%	$105.1271	$105.13	$105.15	$105.10
Purchase #7	$246.63	7.816%	$265.9066	$265.91	$265.90	$265.90
7 purchase totals =	$1,016.89		$1,084.0566	$1,084.07	$1,084.10	$1,084.10