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	$184.33	6.755%	$196.7815	$196.78	$196.80	$196.80
Purchase #2	$218.41	8.691%	$237.392	$237.39	$237.40	$237.40
Purchase #3	$6.71	10.102%	$7.3878	$7.39	$7.40	$7.40
Purchase #4	$199.32	7.310%	$213.8903	$213.89	$213.90	$213.90
Purchase #5	$110.47	10.315%	$121.865	$121.87	$121.85	$121.90
Purchase #6	$73.47	7.164%	$78.7334	$78.73	$78.75	$78.70
Purchase #7	$34.28	13.642%	$38.9565	$38.96	$38.95	$39.00
7 purchase totals =	$826.99		$895.0065	$895.01	$895.05	$895.10