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	$41.31	5.111%	$43.4214	$43.42	$43.40	$43.40
Purchase #2	$114.95	11.707%	$128.4072	$128.41	$128.40	$128.40
Purchase #3	$196.38	6.232%	$208.6184	$208.62	$208.60	$208.60
Purchase #4	$19.53	12.673%	$22.005	$22.01	$22.00	$22.00
Purchase #5	$59.48	11.700%	$66.4392	$66.44	$66.45	$66.40
Purchase #6	$46.71	3.840%	$48.5037	$48.50	$48.50	$48.50
Purchase #7	$250.61	5.575%	$264.5815	$264.58	$264.60	$264.60
7 purchase totals =	$728.97		$781.9764	$781.98	$781.95	$781.90