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	$228.82	5.686%	$241.8307	$241.83	$241.85	$241.80
Purchase #2	$54.84	4.474%	$57.2935	$57.29	$57.30	$57.30
Purchase #3	$18.51	8.610%	$20.1037	$20.10	$20.10	$20.10
Purchase #4	$122.41	3.243%	$126.3798	$126.38	$126.40	$126.40
Purchase #5	$82.31	4.256%	$85.8131	$85.81	$85.80	$85.80
Purchase #6	$15.76	11.440%	$17.5629	$17.56	$17.55	$17.60
Purchase #7	$109.83	12.251%	$123.2853	$123.29	$123.30	$123.30
7 purchase totals =	$632.48		$672.2690	$672.26	$672.30	$672.30