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	$91.25	3.478%	$94.4237	$94.42	$94.40	$94.40
Purchase #2	$40.36	3.801%	$41.8941	$41.89	$41.90	$41.90
Purchase #3	$121.28	8.289%	$131.3329	$131.33	$131.35	$131.30
Purchase #4	$190.72	4.718%	$199.7182	$199.72	$199.70	$199.70
Purchase #5	$150.37	6.136%	$159.5967	$159.60	$159.60	$159.60
Purchase #6	$94.73	6.467%	$100.8562	$100.86	$100.85	$100.90
Purchase #7	$43.87	4.765%	$45.9604	$45.96	$45.95	$46.00
7 purchase totals =	$732.58		$773.7822	$773.78	$773.75	$773.80