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	$42.87	4.844%	$44.9466	$44.95	$44.95	$44.90
Purchase #2	$247.43	12.162%	$277.5224	$277.52	$277.50	$277.50
Purchase #3	$54.66	8.759%	$59.4477	$59.45	$59.45	$59.40
Purchase #4	$137.47	9.484%	$150.5077	$150.51	$150.50	$150.50
Purchase #5	$191.55	4.796%	$200.7367	$200.74	$200.75	$200.70
Purchase #6	$236.41	12.593%	$266.1811	$266.18	$266.20	$266.20
Purchase #7	$39.61	8.411%	$42.9416	$42.94	$42.95	$42.90
7 purchase totals =	$950.00		$1,042.2838	$1,042.29	$1,042.30	$1,042.10