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	$184.37	5.538%	$194.5804	$194.58	$194.60	$194.60
Purchase #2	$80.37	8.181%	$86.9451	$86.95	$86.95	$86.90
Purchase #3	$106.54	11.455%	$118.7442	$118.74	$118.75	$118.70
Purchase #4	$238.56	9.224%	$260.5648	$260.56	$260.55	$260.60
Purchase #5	$199.44	12.177%	$223.7258	$223.73	$223.75	$223.70
Purchase #6	$53.28	10.856%	$59.0641	$59.06	$59.05	$59.10
Purchase #7	$41.92	9.508%	$45.9058	$45.91	$45.90	$45.90
7 purchase totals =	$904.48		$989.5302	$989.53	$989.55	$989.50