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	$37.39	9.465%	$40.929	$40.93	$40.95	$40.90
Purchase #2	$27.32	11.681%	$30.5112	$30.51	$30.50	$30.50
Purchase #3	$91.92	9.146%	$100.327	$100.33	$100.35	$100.30
Purchase #4	$92.61	3.828%	$96.1551	$96.16	$96.15	$96.20
Purchase #5	$13.94	12.779%	$15.7214	$15.72	$15.70	$15.70
Purchase #6	$246.95	5.171%	$259.7198	$259.72	$259.70	$259.70
Purchase #7	$41.39	8.298%	$44.8245	$44.82	$44.80	$44.80
7 purchase totals =	$551.52		$588.1880	$588.19	$588.15	$588.10