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	$80.38	13.527%	$91.253	$91.25	$91.25	$91.30
Purchase #2	$19.94	5.424%	$21.0215	$21.02	$21.00	$21.00
Purchase #3	$168.97	12.575%	$190.218	$190.22	$190.20	$190.20
Purchase #4	$205.84	8.793%	$223.9395	$223.94	$223.95	$223.90
Purchase #5	$86.74	3.107%	$89.435	$89.44	$89.45	$89.40
Purchase #6	$30.59	7.762%	$32.9644	$32.96	$32.95	$33.00
Purchase #7	$50.46	11.154%	$56.0883	$56.09	$56.10	$56.10
7 purchase totals =	$642.92		$704.9197	$704.92	$704.90	$704.90