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	$10.46	4.858%	$10.9681	$10.97	$10.95	$11.00
Purchase #2	$19.82	9.112%	$21.626	$21.63	$21.65	$21.60
Purchase #3	$105.72	10.224%	$116.5288	$116.53	$116.55	$116.50
Purchase #4	$224.61	7.250%	$240.8942	$240.89	$240.90	$240.90
Purchase #5	$138.82	8.400%	$150.4809	$150.48	$150.50	$150.50
Purchase #6	$132.82	9.535%	$145.4844	$145.48	$145.50	$145.50
Purchase #7	$88.70	10.613%	$98.1137	$98.11	$98.10	$98.10
7 purchase totals =	$720.95		$784.0961	$784.09	$784.15	$784.10