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	$184.97	13.318%	$209.6043	$209.60	$209.60	$209.60
Purchase #2	$41.73	5.168%	$43.8866	$43.89	$43.90	$43.90
Purchase #3	$25.59	6.340%	$27.2124	$27.21	$27.20	$27.20
Purchase #4	$89.92	9.568%	$98.5235	$98.52	$98.50	$98.50
Purchase #5	$200.28	13.534%	$227.3859	$227.39	$227.40	$227.40
Purchase #6	$117.25	8.435%	$127.14	$127.14	$127.15	$127.10
Purchase #7	$56.44	7.840%	$60.8649	$60.86	$60.85	$60.90
7 purchase totals =	$716.18		$794.6176	$794.61	$794.60	$794.60