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	$91.37	13.562%	$103.7616	$103.76	$103.75	$103.80
Purchase #2	$31.61	5.340%	$33.298	$33.30	$33.30	$33.30
Purchase #3	$92.33	3.598%	$95.652	$95.65	$95.65	$95.70
Purchase #4	$144.66	9.478%	$158.3709	$158.37	$158.35	$158.40
Purchase #5	$219.97	3.484%	$227.6338	$227.63	$227.65	$227.60
Purchase #6	$48.46	3.473%	$50.143	$50.14	$50.15	$50.10
Purchase #7	$70.85	9.577%	$77.6353	$77.64	$77.65	$77.60
7 purchase totals =	$699.25		$746.4946	$746.49	$746.50	$746.50