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	$61.63	3.697%	$63.9085	$63.91	$63.90	$63.90
Purchase #2	$73.56	7.157%	$78.8247	$78.82	$78.80	$78.80
Purchase #3	$153.83	9.721%	$168.7838	$168.78	$168.80	$168.80
Purchase #4	$83.88	5.858%	$88.7937	$88.79	$88.80	$88.80
Purchase #5	$134.87	11.531%	$150.4219	$150.42	$150.40	$150.40
Purchase #6	$53.59	5.129%	$56.3386	$56.34	$56.35	$56.30
Purchase #7	$137.38	10.610%	$151.956	$151.96	$151.95	$152.00
7 purchase totals =	$698.74		$759.0272	$759.02	$759.00	$759.00