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	$242.31	4.831%	$254.016	$254.02	$254.00	$254.00
Purchase #2	$11.54	3.156%	$11.9042	$11.90	$11.90	$11.90
Purchase #3	$86.46	3.440%	$89.4342	$89.43	$89.45	$89.40
Purchase #4	$81.43	8.225%	$88.1276	$88.13	$88.15	$88.10
Purchase #5	$141.60	9.619%	$155.2205	$155.22	$155.20	$155.20
Purchase #6	$135.51	12.453%	$152.3851	$152.39	$152.40	$152.40
Purchase #7	$56.31	3.777%	$58.4368	$58.44	$58.45	$58.40
7 purchase totals =	$755.16		$809.5244	$809.53	$809.55	$809.40