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	$50.74	7.629%	$54.611	$54.61	$54.60	$54.60
Purchase #2	$174.59	6.567%	$186.0553	$186.06	$186.05	$186.10
Purchase #3	$140.70	4.817%	$147.4775	$147.48	$147.50	$147.50
Purchase #4	$192.88	13.261%	$218.4578	$218.46	$218.45	$218.50
Purchase #5	$214.90	5.688%	$227.1235	$227.12	$227.10	$227.10
Purchase #6	$65.71	7.542%	$70.6658	$70.67	$70.65	$70.70
Purchase #7	$107.73	5.407%	$113.555	$113.56	$113.55	$113.60
7 purchase totals =	$947.25		$1,017.9459	$1,017.96	$1,017.90	$1,018.10