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	$161.46	7.544%	$173.6405	$173.64	$173.65	$173.60
Purchase #2	$29.42	12.300%	$33.0387	$33.04	$33.05	$33.00
Purchase #3	$96.27	9.371%	$105.2915	$105.29	$105.30	$105.30
Purchase #4	$41.27	13.341%	$46.7758	$46.78	$46.80	$46.80
Purchase #5	$91.71	12.464%	$103.1407	$103.14	$103.15	$103.10
Purchase #6	$199.39	7.807%	$214.9564	$214.96	$214.95	$215.00
Purchase #7	$93.66	9.309%	$102.3788	$102.38	$102.40	$102.40
7 purchase totals =	$713.18		$779.2224	$779.23	$779.30	$779.20