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	$96.64	13.659%	$109.8401	$109.84	$109.85	$109.80
Purchase #2	$159.61	12.511%	$179.5788	$179.58	$179.60	$179.60
Purchase #3	$250.71	5.558%	$264.6445	$264.64	$264.65	$264.60
Purchase #4	$69.52	5.437%	$73.2998	$73.30	$73.30	$73.30
Purchase #5	$80.72	10.823%	$89.4563	$89.46	$89.45	$89.50
Purchase #6	$202.94	7.138%	$217.4259	$217.43	$217.45	$217.40
Purchase #7	$59.78	4.776%	$62.6351	$62.64	$62.65	$62.60
7 purchase totals =	$919.92		$996.8805	$996.89	$996.95	$996.80