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	$153.49	10.598%	$169.7569	$169.76	$169.75	$169.80
Purchase #2	$6.69	10.507%	$7.3929	$7.39	$7.40	$7.40
Purchase #3	$178.50	6.339%	$189.8151	$189.82	$189.80	$189.80
Purchase #4	$22.65	4.310%	$23.6262	$23.63	$23.65	$23.60
Purchase #5	$77.89	6.174%	$82.6989	$82.70	$82.70	$82.70
Purchase #6	$128.85	9.394%	$140.9542	$140.95	$140.95	$141.00
Purchase #7	$48.37	9.823%	$53.1214	$53.12	$53.10	$53.10
7 purchase totals =	$616.44		$667.3656	$667.37	$667.35	$667.40