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	$50.54	9.361%	$55.271	$55.27	$55.25	$55.30
Purchase #2	$126.55	13.577%	$143.7317	$143.73	$143.75	$143.70
Purchase #3	$159.83	3.307%	$165.1156	$165.12	$165.10	$165.10
Purchase #4	$54.86	3.128%	$56.576	$56.58	$56.60	$56.60
Purchase #5	$246.36	9.199%	$269.0227	$269.02	$269.00	$269.00
Purchase #6	$11.43	3.736%	$11.857	$11.86	$11.85	$11.90
Purchase #7	$58.91	3.590%	$61.0249	$61.02	$61.00	$61.00
7 purchase totals =	$708.48		$762.5989	$762.60	$762.55	$762.60