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	$83.97	8.776%	$91.3392	$91.34	$91.35	$91.30
Purchase #2	$152.95	10.862%	$169.5634	$169.56	$169.55	$169.60
Purchase #3	$211.89	6.410%	$225.4721	$225.47	$225.45	$225.50
Purchase #4	$211.58	13.307%	$239.735	$239.74	$239.75	$239.70
Purchase #5	$173.45	4.540%	$181.3246	$181.32	$181.30	$181.30
Purchase #6	$45.41	10.443%	$50.1522	$50.15	$50.15	$50.20
Purchase #7	$54.45	3.374%	$56.2871	$56.29	$56.30	$56.30
7 purchase totals =	$933.70		$1,013.8736	$1,013.87	$1,013.85	$1,013.90