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	$183.94	7.235%	$197.2481	$197.25	$197.25	$197.20
Purchase #2	$39.51	6.537%	$42.0928	$42.09	$42.10	$42.10
Purchase #3	$250.35	7.680%	$269.5769	$269.58	$269.60	$269.60
Purchase #4	$163.94	6.709%	$174.9387	$174.94	$174.95	$174.90
Purchase #5	$50.93	12.619%	$57.3569	$57.36	$57.35	$57.40
Purchase #6	$79.36	13.764%	$90.2831	$90.28	$90.30	$90.30
Purchase #7	$82.54	7.851%	$89.0202	$89.02	$89.00	$89.00
7 purchase totals =	$850.57		$920.5167	$920.52	$920.55	$920.50