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	$105.51	3.451%	$109.1512	$109.15	$109.15	$109.20
Purchase #2	$176.47	7.588%	$189.8605	$189.86	$189.85	$189.90
Purchase #3	$174.57	4.340%	$182.1463	$182.15	$182.15	$182.10
Purchase #4	$117.72	5.132%	$123.7614	$123.76	$123.75	$123.80
Purchase #5	$221.60	10.493%	$244.8525	$244.85	$244.85	$244.90
Purchase #6	$17.48	4.705%	$18.3024	$18.30	$18.30	$18.30
Purchase #7	$136.54	13.669%	$155.2037	$155.20	$155.20	$155.20
7 purchase totals =	$949.89		$1,023.2780	$1,023.27	$1,023.25	$1,023.40