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	$103.80	7.736%	$111.83	$111.83	$111.85	$111.80
Purchase #2	$229.71	6.310%	$244.2047	$244.20	$244.20	$244.20
Purchase #3	$14.26	12.300%	$16.014	$16.01	$16.00	$16.00
Purchase #4	$203.59	13.678%	$231.437	$231.44	$231.45	$231.40
Purchase #5	$154.35	4.511%	$161.3127	$161.31	$161.30	$161.30
Purchase #6	$114.70	7.483%	$123.283	$123.28	$123.30	$123.30
Purchase #7	$37.35	9.322%	$40.8318	$40.83	$40.85	$40.80
7 purchase totals =	$857.76		$928.9132	$928.90	$928.95	$928.80