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	$146.59	13.830%	$166.8634	$166.86	$166.85	$166.90
Purchase #2	$109.73	4.129%	$114.2608	$114.26	$114.25	$114.30
Purchase #3	$177.52	12.270%	$199.3017	$199.30	$199.30	$199.30
Purchase #4	$99.62	9.248%	$108.8329	$108.83	$108.85	$108.80
Purchase #5	$31.48	3.123%	$32.4631	$32.46	$32.45	$32.50
Purchase #6	$81.75	6.474%	$87.0425	$87.04	$87.05	$87.00
Purchase #7	$75.31	13.705%	$85.6312	$85.63	$85.65	$85.60
7 purchase totals =	$722.00		$794.3956	$794.38	$794.40	$794.40