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	$229.60	10.568%	$253.8641	$253.86	$253.85	$253.90
Purchase #2	$29.36	10.237%	$32.3656	$32.37	$32.35	$32.40
Purchase #3	$147.33	5.128%	$154.8851	$154.89	$154.90	$154.90
Purchase #4	$222.29	8.429%	$241.0268	$241.03	$241.05	$241.00
Purchase #5	$124.77	13.872%	$142.0781	$142.08	$142.10	$142.10
Purchase #6	$27.33	3.757%	$28.3568	$28.36	$28.35	$28.40
Purchase #7	$198.33	12.821%	$223.7579	$223.76	$223.75	$223.80
7 purchase totals =	$979.01		$1,076.3344	$1,076.35	$1,076.35	$1,076.50