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	$169.40	5.736%	$179.1168	$179.12	$179.10	$179.10
Purchase #2	$84.55	7.458%	$90.8557	$90.86	$90.85	$90.90
Purchase #3	$90.61	9.194%	$98.9407	$98.94	$98.95	$98.90
Purchase #4	$87.87	11.652%	$98.1086	$98.11	$98.10	$98.10
Purchase #5	$180.51	8.604%	$196.0411	$196.04	$196.05	$196.00
Purchase #6	$97.94	4.810%	$102.6509	$102.65	$102.65	$102.70
Purchase #7	$241.48	9.455%	$264.3119	$264.31	$264.30	$264.30
7 purchase totals =	$952.36		$1,030.0257	$1,030.03	$1,030.00	$1,030.00