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	$143.28	11.370%	$159.5709	$159.57	$159.55	$159.60
Purchase #2	$42.37	9.497%	$46.3939	$46.39	$46.40	$46.40
Purchase #3	$84.69	7.279%	$90.8546	$90.85	$90.85	$90.90
Purchase #4	$81.65	8.263%	$88.3967	$88.40	$88.40	$88.40
Purchase #5	$172.55	10.792%	$191.1716	$191.17	$191.15	$191.20
Purchase #6	$156.43	6.800%	$167.0672	$167.07	$167.05	$167.10
Purchase #7	$205.53	8.743%	$223.4995	$223.50	$223.50	$223.50
7 purchase totals =	$886.50		$966.9544	$966.95	$966.90	$967.10