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	$82.35	12.490%	$92.6355	$92.64	$92.65	$92.60
Purchase #2	$224.91	3.335%	$232.4107	$232.41	$232.40	$232.40
Purchase #3	$156.84	12.598%	$176.5987	$176.60	$176.60	$176.60
Purchase #4	$236.72	10.505%	$261.5874	$261.59	$261.60	$261.60
Purchase #5	$105.73	5.192%	$111.2195	$111.22	$111.20	$111.20
Purchase #6	$98.32	10.755%	$108.8943	$108.89	$108.90	$108.90
Purchase #7	$12.36	4.272%	$12.888	$12.89	$12.90	$12.90
7 purchase totals =	$917.23		$996.2341	$996.24	$996.25	$996.20