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	$135.94	4.460%	$142.0029	$142.00	$142.00	$142.00
Purchase #2	$126.30	12.316%	$141.8551	$141.86	$141.85	$141.90
Purchase #3	$50.32	7.484%	$54.0859	$54.09	$54.10	$54.10
Purchase #4	$19.52	11.155%	$21.6975	$21.70	$21.70	$21.70
Purchase #5	$91.27	7.565%	$98.1746	$98.17	$98.15	$98.20
Purchase #6	$80.72	5.764%	$85.3727	$85.37	$85.35	$85.40
Purchase #7	$105.57	4.464%	$110.2826	$110.28	$110.30	$110.30
7 purchase totals =	$609.64		$653.4713	$653.47	$653.45	$653.60