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	$48.46	11.128%	$53.8526	$53.85	$53.85	$53.90
Purchase #2	$50.34	10.510%	$55.6307	$55.63	$55.65	$55.60
Purchase #3	$90.70	7.492%	$97.4952	$97.50	$97.50	$97.50
Purchase #4	$64.72	12.477%	$72.7951	$72.80	$72.80	$72.80
Purchase #5	$228.65	5.284%	$240.7319	$240.73	$240.75	$240.70
Purchase #6	$67.34	13.777%	$76.6174	$76.62	$76.60	$76.60
Purchase #7	$66.86	9.803%	$73.4143	$73.41	$73.40	$73.40
7 purchase totals =	$617.07		$670.5372	$670.54	$670.55	$670.50