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	$52.68	11.671%	$58.8283	$58.83	$58.85	$58.80
Purchase #2	$93.66	7.479%	$100.6648	$100.66	$100.65	$100.70
Purchase #3	$200.93	10.492%	$222.0116	$222.01	$222.00	$222.00
Purchase #4	$201.76	11.721%	$225.4083	$225.41	$225.40	$225.40
Purchase #5	$54.46	3.409%	$56.3165	$56.32	$56.30	$56.30
Purchase #6	$92.88	8.149%	$100.4488	$100.45	$100.45	$100.40
Purchase #7	$27.81	4.415%	$29.0378	$29.04	$29.05	$29.00
7 purchase totals =	$724.18		$792.7161	$792.72	$792.70	$792.60