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	$40.95	13.464%	$46.4635	$46.46	$46.45	$46.50
Purchase #2	$139.26	9.178%	$152.0413	$152.04	$152.05	$152.00
Purchase #3	$119.92	9.569%	$131.3951	$131.40	$131.40	$131.40
Purchase #4	$40.72	6.646%	$43.4263	$43.43	$43.45	$43.40
Purchase #5	$82.72	8.824%	$90.0192	$90.02	$90.00	$90.00
Purchase #6	$88.61	13.872%	$100.902	$100.90	$100.90	$100.90
Purchase #7	$175.30	6.862%	$187.3291	$187.33	$187.35	$187.30
7 purchase totals =	$687.48		$751.5765	$751.58	$751.60	$751.50