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	$93.48	5.459%	$98.5831	$98.58	$98.60	$98.60
Purchase #2	$127.78	7.764%	$137.7008	$137.70	$137.70	$137.70
Purchase #3	$50.42	5.545%	$53.2158	$53.22	$53.20	$53.20
Purchase #4	$6.31	4.545%	$6.5968	$6.60	$6.60	$6.60
Purchase #5	$115.48	13.774%	$131.3862	$131.39	$131.40	$131.40
Purchase #6	$77.64	5.155%	$81.6423	$81.64	$81.65	$81.60
Purchase #7	$246.41	7.729%	$265.455	$265.46	$265.45	$265.50
7 purchase totals =	$717.52		$774.5800	$774.59	$774.60	$774.60