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	$207.37	7.146%	$222.1887	$222.19	$222.20	$222.20
Purchase #2	$222.80	8.356%	$241.4172	$241.42	$241.40	$241.40
Purchase #3	$37.83	11.593%	$42.2156	$42.22	$42.20	$42.20
Purchase #4	$125.80	8.125%	$136.0213	$136.02	$136.00	$136.00
Purchase #5	$120.43	6.627%	$128.4109	$128.41	$128.40	$128.40
Purchase #6	$221.76	4.360%	$231.4287	$231.43	$231.45	$231.40
Purchase #7	$13.59	7.300%	$14.5821	$14.58	$14.60	$14.60
7 purchase totals =	$949.58		$1,016.2645	$1,016.27	$1,016.25	$1,016.20