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	$133.79	12.288%	$150.2301	$150.23	$150.25	$150.20
Purchase #2	$130.69	8.837%	$142.2391	$142.24	$142.25	$142.20
Purchase #3	$34.87	6.323%	$37.0748	$37.07	$37.05	$37.10
Purchase #4	$200.49	12.302%	$225.1543	$225.15	$225.15	$225.20
Purchase #5	$238.63	6.325%	$253.7233	$253.72	$253.70	$253.70
Purchase #6	$99.78	9.243%	$109.0027	$109.00	$109.00	$109.00
Purchase #7	$109.41	13.226%	$123.8806	$123.88	$123.90	$123.90
7 purchase totals =	$947.66		$1,041.3049	$1,041.29	$1,041.30	$1,041.30