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	$243.43	6.279%	$258.715	$258.72	$258.70	$258.70
Purchase #2	$36.76	11.117%	$40.8466	$40.85	$40.85	$40.80
Purchase #3	$72.72	10.737%	$80.5279	$80.53	$80.55	$80.50
Purchase #4	$217.64	5.149%	$228.8463	$228.85	$228.85	$228.80
Purchase #5	$212.91	3.533%	$220.4321	$220.43	$220.45	$220.40
Purchase #6	$131.62	11.723%	$147.0498	$147.05	$147.05	$147.00
Purchase #7	$33.97	11.207%	$37.777	$37.78	$37.80	$37.80
7 purchase totals =	$949.05		$1,014.1947	$1,014.21	$1,014.25	$1,014.00