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	$97.56	8.536%	$105.8877	$105.89	$105.90	$105.90
Purchase #2	$96.92	7.829%	$104.5079	$104.51	$104.50	$104.50
Purchase #3	$21.98	3.380%	$22.7229	$22.72	$22.70	$22.70
Purchase #4	$179.33	6.134%	$190.3301	$190.33	$190.35	$190.30
Purchase #5	$56.40	13.810%	$64.1888	$64.19	$64.20	$64.20
Purchase #6	$128.49	12.711%	$144.8224	$144.82	$144.80	$144.80
Purchase #7	$241.93	11.341%	$269.3673	$269.37	$269.35	$269.40
7 purchase totals =	$822.61		$901.8271	$901.83	$901.80	$901.80