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	$95.30	5.117%	$100.1765	$100.18	$100.20	$100.20
Purchase #2	$87.73	4.234%	$91.4445	$91.44	$91.45	$91.40
Purchase #3	$13.46	5.207%	$14.1609	$14.16	$14.15	$14.20
Purchase #4	$118.71	10.480%	$131.1508	$131.15	$131.15	$131.20
Purchase #5	$103.76	3.462%	$107.3522	$107.35	$107.35	$107.40
Purchase #6	$64.62	12.300%	$72.5683	$72.57	$72.55	$72.60
Purchase #7	$37.75	9.363%	$41.2845	$41.28	$41.30	$41.30
7 purchase totals =	$521.33		$558.1377	$558.13	$558.15	$558.30