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	$103.31	11.159%	$114.8384	$114.84	$114.85	$114.80
Purchase #2	$196.98	8.582%	$213.8848	$213.88	$213.90	$213.90
Purchase #3	$197.83	3.767%	$205.2823	$205.28	$205.30	$205.30
Purchase #4	$12.42	9.325%	$13.5782	$13.58	$13.60	$13.60
Purchase #5	$181.85	8.267%	$196.8835	$196.88	$196.90	$196.90
Purchase #6	$143.80	3.854%	$149.3421	$149.34	$149.35	$149.30
Purchase #7	$92.46	13.668%	$105.0974	$105.10	$105.10	$105.10
7 purchase totals =	$928.65		$998.9067	$998.90	$999.00	$998.90