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	$118.54	3.366%	$122.5301	$122.53	$122.55	$122.50
Purchase #2	$6.31	9.467%	$6.9074	$6.91	$6.90	$6.90
Purchase #3	$171.69	11.817%	$191.9786	$191.98	$192.00	$192.00
Purchase #4	$39.50	8.570%	$42.8852	$42.89	$42.90	$42.90
Purchase #5	$48.46	5.500%	$51.1253	$51.13	$51.15	$51.10
Purchase #6	$131.66	4.310%	$137.3345	$137.33	$137.35	$137.30
Purchase #7	$16.63	5.135%	$17.484	$17.48	$17.50	$17.50
7 purchase totals =	$532.79		$570.2451	$570.25	$570.35	$570.20