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	$61.37	5.130%	$64.5183	$64.52	$64.50	$64.50
Purchase #2	$86.62	12.702%	$97.6225	$97.62	$97.60	$97.60
Purchase #3	$162.60	13.453%	$184.4746	$184.47	$184.45	$184.50
Purchase #4	$155.61	8.814%	$169.3255	$169.33	$169.35	$169.30
Purchase #5	$80.84	6.451%	$86.055	$86.06	$86.05	$86.10
Purchase #6	$69.78	3.172%	$71.9934	$71.99	$72.00	$72.00
Purchase #7	$204.63	9.188%	$223.4314	$223.43	$223.45	$223.40
7 purchase totals =	$821.45		$897.4207	$897.42	$897.40	$897.40