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	$233.81	12.577%	$263.2163	$263.22	$263.20	$263.20
Purchase #2	$43.39	4.118%	$45.1768	$45.18	$45.20	$45.20
Purchase #3	$76.95	8.546%	$83.5261	$83.53	$83.55	$83.50
Purchase #4	$90.79	4.818%	$95.1643	$95.16	$95.15	$95.20
Purchase #5	$196.77	4.224%	$205.0816	$205.08	$205.10	$205.10
Purchase #6	$48.31	6.720%	$51.5564	$51.56	$51.55	$51.60
Purchase #7	$94.89	8.484%	$102.9405	$102.94	$102.95	$102.90
7 purchase totals =	$784.91		$846.6620	$846.67	$846.70	$846.70