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	$39.43	4.747%	$41.3017	$41.30	$41.30	$41.30
Purchase #2	$95.90	9.621%	$105.1265	$105.13	$105.15	$105.10
Purchase #3	$161.66	8.235%	$174.9727	$174.97	$174.95	$175.00
Purchase #4	$88.91	12.612%	$100.1233	$100.12	$100.10	$100.10
Purchase #5	$97.50	7.854%	$105.1577	$105.16	$105.15	$105.20
Purchase #6	$19.28	4.136%	$20.0774	$20.08	$20.10	$20.10
Purchase #7	$145.33	9.113%	$158.5739	$158.57	$158.55	$158.60
7 purchase totals =	$648.01		$705.3332	$705.33	$705.30	$705.40