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	$230.94	5.493%	$243.6255	$243.63	$243.65	$243.60
Purchase #2	$247.68	10.455%	$273.5749	$273.57	$273.55	$273.60
Purchase #3	$55.31	8.324%	$59.914	$59.91	$59.90	$59.90
Purchase #4	$142.40	11.151%	$158.279	$158.28	$158.30	$158.30
Purchase #5	$33.30	13.280%	$37.7222	$37.72	$37.70	$37.70
Purchase #6	$49.75	7.480%	$53.4713	$53.47	$53.45	$53.50
Purchase #7	$20.89	7.244%	$22.4033	$22.40	$22.40	$22.40
7 purchase totals =	$780.27		$848.9902	$848.98	$848.95	$849.00