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	$213.56	13.262%	$241.8823	$241.88	$241.90	$241.90
Purchase #2	$9.83	8.749%	$10.69	$10.69	$10.70	$10.70
Purchase #3	$152.61	8.248%	$165.1973	$165.20	$165.20	$165.20
Purchase #4	$246.83	6.440%	$262.7259	$262.73	$262.75	$262.70
Purchase #5	$158.71	9.202%	$173.3145	$173.31	$173.30	$173.30
Purchase #6	$177.28	10.697%	$196.2436	$196.24	$196.25	$196.20
Purchase #7	$37.84	6.579%	$40.3295	$40.33	$40.35	$40.30
7 purchase totals =	$996.66		$1,090.3831	$1,090.38	$1,090.45	$1,090.30