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	$231.36	6.276%	$245.8802	$245.88	$245.90	$245.90
Purchase #2	$64.72	12.296%	$72.678	$72.68	$72.70	$72.70
Purchase #3	$86.30	3.840%	$89.6139	$89.61	$89.60	$89.60
Purchase #4	$117.88	5.289%	$124.1147	$124.11	$124.10	$124.10
Purchase #5	$139.33	8.621%	$151.3416	$151.34	$151.35	$151.30
Purchase #6	$56.80	7.669%	$61.156	$61.16	$61.15	$61.20
Purchase #7	$202.49	4.680%	$211.9665	$211.97	$211.95	$212.00
7 purchase totals =	$898.88		$956.7509	$956.75	$956.75	$956.80