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	$195.36	11.690%	$218.1976	$218.20	$218.20	$218.20
Purchase #2	$45.42	3.165%	$46.8575	$46.86	$46.85	$46.90
Purchase #3	$176.33	4.285%	$183.8857	$183.89	$183.90	$183.90
Purchase #4	$50.36	7.258%	$54.0151	$54.02	$54.00	$54.00
Purchase #5	$163.62	5.404%	$172.462	$172.46	$172.45	$172.50
Purchase #6	$57.27	4.484%	$59.838	$59.84	$59.85	$59.80
Purchase #7	$248.33	13.600%	$282.1029	$282.10	$282.10	$282.10
7 purchase totals =	$936.69		$1,017.3588	$1,017.37	$1,017.35	$1,017.40