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	$87.33	4.595%	$91.3428	$91.34	$91.35	$91.30
Purchase #2	$91.55	4.562%	$95.7265	$95.73	$95.75	$95.70
Purchase #3	$129.32	5.469%	$136.3925	$136.39	$136.40	$136.40
Purchase #4	$26.40	8.486%	$28.6403	$28.64	$28.65	$28.60
Purchase #5	$59.49	10.865%	$65.9536	$65.95	$65.95	$66.00
Purchase #6	$38.82	4.583%	$40.5991	$40.60	$40.60	$40.60
Purchase #7	$201.38	4.814%	$211.0744	$211.07	$211.05	$211.10
7 purchase totals =	$634.29		$669.7292	$669.72	$669.75	$669.70