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	$59.35	7.852%	$64.0102	$64.01	$64.00	$64.00
Purchase #2	$52.42	6.269%	$55.7062	$55.71	$55.70	$55.70
Purchase #3	$80.69	12.201%	$90.535	$90.54	$90.55	$90.50
Purchase #4	$179.88	4.644%	$188.2336	$188.23	$188.25	$188.20
Purchase #5	$150.96	5.353%	$159.0409	$159.04	$159.05	$159.00
Purchase #6	$160.87	7.495%	$172.9272	$172.93	$172.95	$172.90
Purchase #7	$213.39	9.497%	$233.6556	$233.66	$233.65	$233.70
7 purchase totals =	$897.56		$964.1087	$964.12	$964.15	$964.00