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	$53.48	10.692%	$59.1981	$59.20	$59.20	$59.20
Purchase #2	$134.65	11.605%	$150.2761	$150.28	$150.30	$150.30
Purchase #3	$137.55	6.789%	$146.8883	$146.89	$146.90	$146.90
Purchase #4	$233.41	12.477%	$262.5326	$262.53	$262.55	$262.50
Purchase #5	$235.68	8.124%	$254.8266	$254.83	$254.85	$254.80
Purchase #6	$243.88	7.106%	$261.2101	$261.21	$261.20	$261.20
Purchase #7	$104.56	4.701%	$109.4754	$109.48	$109.50	$109.50
7 purchase totals =	$1,143.21		$1,244.4072	$1,244.42	$1,244.50	$1,244.40