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	$55.84	9.686%	$61.2487	$61.25	$61.25	$61.20
Purchase #2	$126.27	3.352%	$130.5026	$130.50	$130.50	$130.50
Purchase #3	$48.84	6.691%	$52.1079	$52.11	$52.10	$52.10
Purchase #4	$248.88	12.377%	$279.6839	$279.68	$279.70	$279.70
Purchase #5	$241.85	11.480%	$269.6144	$269.61	$269.60	$269.60
Purchase #6	$19.94	3.766%	$20.6909	$20.69	$20.70	$20.70
Purchase #7	$30.51	3.241%	$31.4988	$31.50	$31.50	$31.50
7 purchase totals =	$772.13		$845.3472	$845.34	$845.35	$845.30