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	$100.69	12.168%	$112.942	$112.94	$112.95	$112.90
Purchase #2	$137.71	8.269%	$149.0972	$149.10	$149.10	$149.10
Purchase #3	$133.45	13.585%	$151.5792	$151.58	$151.60	$151.60
Purchase #4	$240.59	13.837%	$273.8804	$273.88	$273.90	$273.90
Purchase #5	$231.55	11.694%	$258.6275	$258.63	$258.65	$258.60
Purchase #6	$85.74	3.869%	$89.0573	$89.06	$89.05	$89.10
Purchase #7	$104.88	13.860%	$119.4164	$119.42	$119.40	$119.40
7 purchase totals =	$1,034.61		$1,154.6000	$1,154.61	$1,154.65	$1,154.60