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	$132.79	11.420%	$147.9546	$147.95	$147.95	$148.00
Purchase #2	$129.46	13.332%	$146.7196	$146.72	$146.70	$146.70
Purchase #3	$103.98	13.336%	$117.8468	$117.85	$117.85	$117.80
Purchase #4	$39.94	7.437%	$42.9103	$42.91	$42.90	$42.90
Purchase #5	$24.92	6.190%	$26.4625	$26.46	$26.45	$26.50
Purchase #6	$196.43	13.804%	$223.5452	$223.55	$223.55	$223.50
Purchase #7	$103.89	7.536%	$111.7192	$111.72	$111.70	$111.70
7 purchase totals =	$731.41		$817.1582	$817.16	$817.10	$817.10