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	$124.31	5.833%	$131.561	$131.56	$131.55	$131.60
Purchase #2	$143.59	10.651%	$158.8838	$158.88	$158.90	$158.90
Purchase #3	$150.83	8.760%	$164.0427	$164.04	$164.05	$164.00
Purchase #4	$146.37	10.391%	$161.5793	$161.58	$161.60	$161.60
Purchase #5	$110.69	10.334%	$122.1287	$122.13	$122.15	$122.10
Purchase #6	$80.42	11.525%	$89.6884	$89.69	$89.70	$89.70
Purchase #7	$202.90	7.627%	$218.3752	$218.38	$218.40	$218.40
7 purchase totals =	$959.11		$1,046.2591	$1,046.26	$1,046.35	$1,046.30