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	$140.86	12.525%	$158.5027	$158.50	$158.50	$158.50
Purchase #2	$41.69	12.181%	$46.7683	$46.77	$46.75	$46.80
Purchase #3	$182.54	4.152%	$190.1191	$190.12	$190.10	$190.10
Purchase #4	$87.42	9.841%	$96.023	$96.02	$96.00	$96.00
Purchase #5	$140.37	5.178%	$147.6384	$147.64	$147.65	$147.60
Purchase #6	$136.89	10.318%	$151.0143	$151.01	$151.00	$151.00
Purchase #7	$46.58	10.801%	$51.6111	$51.61	$51.60	$51.60
7 purchase totals =	$776.35		$841.6769	$841.67	$841.60	$841.60