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	$100.90	9.360%	$110.3442	$110.34	$110.35	$110.30
Purchase #2	$145.57	8.272%	$157.6116	$157.61	$157.60	$157.60
Purchase #3	$154.40	13.789%	$175.6902	$175.69	$175.70	$175.70
Purchase #4	$247.33	12.598%	$278.4886	$278.49	$278.50	$278.50
Purchase #5	$167.73	7.103%	$179.6439	$179.64	$179.65	$179.60
Purchase #6	$79.34	13.322%	$89.9097	$89.91	$89.90	$89.90
Purchase #7	$46.25	12.470%	$52.0174	$52.02	$52.00	$52.00
7 purchase totals =	$941.52		$1,043.7056	$1,043.70	$1,043.70	$1,043.60