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	$127.59	4.671%	$133.5497	$133.55	$133.55	$133.50
Purchase #2	$207.57	9.567%	$227.4282	$227.43	$227.45	$227.40
Purchase #3	$100.31	5.870%	$106.1982	$106.20	$106.20	$106.20
Purchase #4	$161.65	13.444%	$183.3822	$183.38	$183.40	$183.40
Purchase #5	$109.47	12.355%	$122.995	$123.00	$123.00	$123.00
Purchase #6	$224.61	11.483%	$250.402	$250.40	$250.40	$250.40
Purchase #7	$120.54	13.314%	$136.5887	$136.59	$136.60	$136.60
7 purchase totals =	$1,051.74		$1,160.5440	$1,160.55	$1,160.60	$1,160.50