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	$233.97	11.741%	$261.4404	$261.44	$261.45	$261.40
Purchase #2	$33.98	11.621%	$37.9288	$37.93	$37.95	$37.90
Purchase #3	$46.63	4.498%	$48.7274	$48.73	$48.75	$48.70
Purchase #4	$80.46	3.512%	$83.2858	$83.29	$83.30	$83.30
Purchase #5	$13.87	4.322%	$14.4695	$14.47	$14.45	$14.50
Purchase #6	$81.76	10.211%	$90.1085	$90.11	$90.10	$90.10
Purchase #7	$187.89	4.572%	$196.4803	$196.48	$196.50	$196.50
7 purchase totals =	$678.56		$732.4407	$732.45	$732.50	$732.40