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	$82.56	10.573%	$91.2891	$91.29	$91.30	$91.30
Purchase #2	$201.31	12.128%	$225.7249	$225.72	$225.70	$225.70
Purchase #3	$158.35	12.684%	$178.4351	$178.44	$178.45	$178.40
Purchase #4	$146.51	12.190%	$164.3696	$164.37	$164.35	$164.40
Purchase #5	$181.85	7.799%	$196.0325	$196.03	$196.05	$196.00
Purchase #6	$165.74	3.248%	$171.1232	$171.12	$171.10	$171.10
Purchase #7	$126.82	6.319%	$134.8338	$134.83	$134.85	$134.80
7 purchase totals =	$1,063.14		$1,161.8082	$1,161.80	$1,161.80	$1,161.70