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	$62.58	4.263%	$65.2478	$65.25	$65.25	$65.20
Purchase #2	$128.34	6.756%	$137.0107	$137.01	$137.00	$137.00
Purchase #3	$136.66	6.659%	$145.7602	$145.76	$145.75	$145.80
Purchase #4	$165.78	10.704%	$183.5251	$183.53	$183.55	$183.50
Purchase #5	$84.70	6.109%	$89.8743	$89.87	$89.85	$89.90
Purchase #6	$159.51	11.342%	$177.6016	$177.60	$177.60	$177.60
Purchase #7	$43.96	6.657%	$46.8864	$46.89	$46.90	$46.90
7 purchase totals =	$781.53		$845.9061	$845.91	$845.90	$845.90