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	$91.90	8.630%	$99.831	$99.83	$99.85	$99.80
Purchase #2	$6.47	13.145%	$7.3205	$7.32	$7.30	$7.30
Purchase #3	$167.51	13.194%	$189.6113	$189.61	$189.60	$189.60
Purchase #4	$199.75	12.658%	$225.0344	$225.03	$225.05	$225.00
Purchase #5	$85.91	4.351%	$89.6479	$89.65	$89.65	$89.60
Purchase #6	$82.53	8.376%	$89.4427	$89.44	$89.45	$89.40
Purchase #7	$153.58	11.448%	$171.1618	$171.16	$171.15	$171.20
7 purchase totals =	$787.65		$872.0496	$872.04	$872.05	$871.90