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	$98.68	4.400%	$103.0219	$103.02	$103.00	$103.00
Purchase #2	$23.30	11.151%	$25.8982	$25.90	$25.90	$25.90
Purchase #3	$217.35	9.149%	$237.2354	$237.24	$237.25	$237.20
Purchase #4	$83.30	8.814%	$90.6421	$90.64	$90.65	$90.60
Purchase #5	$92.58	13.730%	$105.2912	$105.29	$105.30	$105.30
Purchase #6	$243.71	9.111%	$265.9144	$265.91	$265.90	$265.90
Purchase #7	$25.45	8.245%	$27.5484	$27.55	$27.55	$27.50
7 purchase totals =	$784.37		$855.5516	$855.55	$855.55	$855.40