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	$105.57	7.340%	$113.3188	$113.32	$113.30	$113.30
Purchase #2	$42.46	7.410%	$45.6063	$45.61	$45.60	$45.60
Purchase #3	$34.98	9.730%	$38.3836	$38.38	$38.40	$38.40
Purchase #4	$250.67	6.731%	$267.5426	$267.54	$267.55	$267.50
Purchase #5	$73.42	4.782%	$76.9309	$76.93	$76.95	$76.90
Purchase #6	$85.49	4.731%	$89.5345	$89.53	$89.55	$89.50
Purchase #7	$71.42	8.315%	$77.3586	$77.36	$77.35	$77.40
7 purchase totals =	$664.01		$708.6753	$708.67	$708.70	$708.60