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	$145.72	13.199%	$164.9536	$164.95	$164.95	$165.00
Purchase #2	$142.73	6.244%	$151.6421	$151.64	$151.65	$151.60
Purchase #3	$218.61	5.454%	$230.533	$230.53	$230.55	$230.50
Purchase #4	$248.86	5.286%	$262.0147	$262.01	$262.00	$262.00
Purchase #5	$174.57	6.850%	$186.528	$186.53	$186.55	$186.50
Purchase #6	$17.70	6.681%	$18.8825	$18.88	$18.90	$18.90
Purchase #7	$129.72	8.601%	$140.8772	$140.88	$140.90	$140.90
7 purchase totals =	$1,077.91		$1,155.4311	$1,155.42	$1,155.50	$1,155.40