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	$83.66	3.107%	$86.2593	$86.26	$86.25	$86.30
Purchase #2	$31.56	3.191%	$32.5671	$32.57	$32.55	$32.60
Purchase #3	$244.81	12.591%	$275.634	$275.63	$275.65	$275.60
Purchase #4	$48.78	6.397%	$51.9005	$51.90	$51.90	$51.90
Purchase #5	$243.55	13.589%	$276.646	$276.65	$276.65	$276.60
Purchase #6	$73.84	9.139%	$80.5882	$80.59	$80.60	$80.60
Purchase #7	$135.66	6.401%	$144.3436	$144.34	$144.35	$144.30
7 purchase totals =	$861.86		$947.9387	$947.94	$947.95	$947.90