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	$123.75	10.169%	$136.3341	$136.33	$136.35	$136.30
Purchase #2	$13.77	8.210%	$14.9005	$14.90	$14.90	$14.90
Purchase #3	$54.73	4.474%	$57.1786	$57.18	$57.20	$57.20
Purchase #4	$214.48	3.515%	$222.019	$222.02	$222.00	$222.00
Purchase #5	$88.67	13.272%	$100.4383	$100.44	$100.45	$100.40
Purchase #6	$77.67	13.542%	$88.1881	$88.19	$88.20	$88.20
Purchase #7	$235.82	3.195%	$243.3544	$243.35	$243.35	$243.40
7 purchase totals =	$808.89		$862.4130	$862.41	$862.45	$862.40