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	$12.83	10.298%	$14.1512	$14.15	$14.15	$14.20
Purchase #2	$70.49	11.562%	$78.6401	$78.64	$78.65	$78.60
Purchase #3	$37.36	10.642%	$41.3359	$41.34	$41.35	$41.30
Purchase #4	$147.75	6.825%	$157.8339	$157.83	$157.85	$157.80
Purchase #5	$71.65	6.192%	$76.0866	$76.09	$76.10	$76.10
Purchase #6	$169.82	11.837%	$189.9216	$189.92	$189.90	$189.90
Purchase #7	$73.88	6.264%	$78.5078	$78.51	$78.50	$78.50
7 purchase totals =	$583.78		$636.4771	$636.48	$636.50	$636.40