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	$190.50	3.158%	$196.516	$196.52	$196.50	$196.50
Purchase #2	$32.52	10.702%	$36.0003	$36.00	$36.00	$36.00
Purchase #3	$216.43	3.583%	$224.1847	$224.18	$224.20	$224.20
Purchase #4	$13.34	11.520%	$14.8768	$14.88	$14.90	$14.90
Purchase #5	$186.30	3.302%	$192.4516	$192.45	$192.45	$192.50
Purchase #6	$173.27	9.313%	$189.4066	$189.41	$189.40	$189.40
Purchase #7	$191.95	6.499%	$204.4248	$204.42	$204.40	$204.40
7 purchase totals =	$1,004.31		$1,057.8608	$1,057.86	$1,057.85	$1,057.90