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	$162.71	11.494%	$181.4119	$181.41	$181.40	$181.40
Purchase #2	$143.37	3.837%	$148.8711	$148.87	$148.85	$148.90
Purchase #3	$13.37	9.164%	$14.5952	$14.60	$14.60	$14.60
Purchase #4	$100.56	3.199%	$103.7769	$103.78	$103.80	$103.80
Purchase #5	$13.29	4.872%	$13.9375	$13.94	$13.95	$13.90
Purchase #6	$96.65	13.491%	$109.6891	$109.69	$109.70	$109.70
Purchase #7	$228.67	13.156%	$258.7538	$258.75	$258.75	$258.80
7 purchase totals =	$758.62		$831.0355	$831.04	$831.05	$831.10