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	$73.59	3.379%	$76.0766	$76.08	$76.10	$76.10
Purchase #2	$89.40	9.479%	$97.8742	$97.87	$97.85	$97.90
Purchase #3	$250.70	5.618%	$264.7843	$264.78	$264.80	$264.80
Purchase #4	$172.39	13.813%	$196.2022	$196.20	$196.20	$196.20
Purchase #5	$31.67	3.249%	$32.699	$32.70	$32.70	$32.70
Purchase #6	$124.97	13.387%	$141.6997	$141.70	$141.70	$141.70
Purchase #7	$241.76	5.293%	$254.5564	$254.56	$254.55	$254.60
7 purchase totals =	$984.48		$1,063.8924	$1,063.89	$1,063.90	$1,064.00