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	$179.40	9.350%	$196.1739	$196.17	$196.15	$196.20
Purchase #2	$36.63	4.783%	$38.382	$38.38	$38.40	$38.40
Purchase #3	$234.37	6.865%	$250.4595	$250.46	$250.45	$250.50
Purchase #4	$223.81	13.248%	$253.4603	$253.46	$253.45	$253.50
Purchase #5	$151.78	7.774%	$163.5794	$163.58	$163.60	$163.60
Purchase #6	$20.70	11.434%	$23.0668	$23.07	$23.05	$23.10
Purchase #7	$89.44	12.134%	$100.2926	$100.29	$100.30	$100.30
7 purchase totals =	$936.13		$1,025.4145	$1,025.41	$1,025.40	$1,025.60