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	$224.35	8.708%	$243.8864	$243.89	$243.90	$243.90
Purchase #2	$72.43	3.457%	$74.9339	$74.93	$74.95	$74.90
Purchase #3	$171.99	11.352%	$191.5143	$191.51	$191.50	$191.50
Purchase #4	$18.79	4.503%	$19.6361	$19.64	$19.65	$19.60
Purchase #5	$53.32	11.120%	$59.2492	$59.25	$59.25	$59.20
Purchase #6	$95.95	10.377%	$105.9067	$105.91	$105.90	$105.90
Purchase #7	$11.58	10.122%	$12.7521	$12.75	$12.75	$12.80
7 purchase totals =	$648.41		$707.8787	$707.88	$707.90	$707.80