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	$250.72	5.343%	$264.116	$264.12	$264.10	$264.10
Purchase #2	$74.77	11.400%	$83.2938	$83.29	$83.30	$83.30
Purchase #3	$157.72	6.696%	$168.2809	$168.28	$168.30	$168.30
Purchase #4	$10.51	12.775%	$11.8527	$11.85	$11.85	$11.90
Purchase #5	$109.58	3.284%	$113.1786	$113.18	$113.20	$113.20
Purchase #6	$234.36	8.731%	$254.822	$254.82	$254.80	$254.80
Purchase #7	$102.27	7.361%	$109.7981	$109.80	$109.80	$109.80
7 purchase totals =	$939.93		$1,005.3421	$1,005.34	$1,005.35	$1,005.40