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	$13.54	6.225%	$14.3829	$14.38	$14.40	$14.40
Purchase #2	$233.62	13.213%	$264.4882	$264.49	$264.50	$264.50
Purchase #3	$179.76	5.610%	$189.8445	$189.84	$189.85	$189.80
Purchase #4	$76.75	7.776%	$82.7181	$82.72	$82.70	$82.70
Purchase #5	$47.58	6.866%	$50.8468	$50.85	$50.85	$50.80
Purchase #6	$68.94	6.155%	$73.1833	$73.18	$73.20	$73.20
Purchase #7	$47.47	9.595%	$52.0247	$52.02	$52.00	$52.00
7 purchase totals =	$667.66		$727.4885	$727.48	$727.50	$727.40