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	$50.81	9.735%	$55.7564	$55.76	$55.75	$55.80
Purchase #2	$76.74	12.157%	$86.0693	$86.07	$86.05	$86.10
Purchase #3	$33.84	13.719%	$38.4825	$38.48	$38.50	$38.50
Purchase #4	$146.43	9.449%	$160.2662	$160.27	$160.25	$160.30
Purchase #5	$248.54	12.766%	$280.2686	$280.27	$280.25	$280.30
Purchase #6	$154.44	4.614%	$161.5659	$161.57	$161.55	$161.60
Purchase #7	$231.89	4.699%	$242.7865	$242.79	$242.80	$242.80
7 purchase totals =	$942.69		$1,025.1954	$1,025.21	$1,025.15	$1,025.40