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	$182.65	4.451%	$190.7798	$190.78	$190.80	$190.80
Purchase #2	$195.59	11.243%	$217.5802	$217.58	$217.60	$217.60
Purchase #3	$63.58	4.678%	$66.5543	$66.55	$66.55	$66.60
Purchase #4	$242.73	8.463%	$263.2722	$263.27	$263.25	$263.30
Purchase #5	$18.83	9.752%	$20.6663	$20.67	$20.65	$20.70
Purchase #6	$175.44	7.663%	$188.884	$188.88	$188.90	$188.90
Purchase #7	$136.78	3.329%	$141.3334	$141.33	$141.35	$141.30
7 purchase totals =	$1,015.60		$1,089.0702	$1,089.06	$1,089.10	$1,089.20