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	$78.33	10.246%	$86.3557	$86.36	$86.35	$86.40
Purchase #2	$39.38	3.614%	$40.8032	$40.80	$40.80	$40.80
Purchase #3	$61.41	3.133%	$63.334	$63.33	$63.35	$63.30
Purchase #4	$110.56	6.869%	$118.1544	$118.15	$118.15	$118.20
Purchase #5	$216.46	9.208%	$236.3916	$236.39	$236.40	$236.40
Purchase #6	$146.34	6.516%	$155.8755	$155.88	$155.90	$155.90
Purchase #7	$29.40	5.785%	$31.1008	$31.10	$31.10	$31.10
7 purchase totals =	$681.88		$732.0152	$732.01	$732.05	$732.10