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	$74.41	11.416%	$82.9046	$82.90	$82.90	$82.90
Purchase #2	$137.82	7.760%	$148.5148	$148.51	$148.50	$148.50
Purchase #3	$204.30	8.574%	$221.8167	$221.82	$221.80	$221.80
Purchase #4	$36.40	3.626%	$37.7199	$37.72	$37.70	$37.70
Purchase #5	$191.38	3.702%	$198.4649	$198.46	$198.45	$198.50
Purchase #6	$224.79	12.462%	$252.8033	$252.80	$252.80	$252.80
Purchase #7	$231.73	9.664%	$254.1244	$254.12	$254.10	$254.10
7 purchase totals =	$1,100.83		$1,196.3486	$1,196.33	$1,196.25	$1,196.30