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	$181.33	8.313%	$196.404	$196.40	$196.40	$196.40
Purchase #2	$87.86	12.178%	$98.5596	$98.56	$98.55	$98.60
Purchase #3	$20.60	5.206%	$21.6724	$21.67	$21.65	$21.70
Purchase #4	$84.78	6.133%	$89.9796	$89.98	$90.00	$90.00
Purchase #5	$15.49	8.872%	$16.8643	$16.86	$16.85	$16.90
Purchase #6	$203.60	12.502%	$229.0541	$229.05	$229.05	$229.10
Purchase #7	$143.43	4.130%	$149.3537	$149.35	$149.35	$149.40
7 purchase totals =	$737.09		$801.8877	$801.87	$801.85	$802.10