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	$148.80	13.218%	$168.4684	$168.47	$168.45	$168.50
Purchase #2	$17.90	9.404%	$19.5833	$19.58	$19.60	$19.60
Purchase #3	$201.47	3.811%	$209.148	$209.15	$209.15	$209.10
Purchase #4	$125.43	4.572%	$131.1647	$131.16	$131.15	$131.20
Purchase #5	$205.95	12.757%	$232.223	$232.22	$232.20	$232.20
Purchase #6	$167.76	7.283%	$179.978	$179.98	$180.00	$180.00
Purchase #7	$71.70	7.763%	$77.2661	$77.27	$77.25	$77.30
7 purchase totals =	$939.01		$1,017.8315	$1,017.83	$1,017.80	$1,017.90