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	$205.52	8.865%	$223.7393	$223.74	$223.75	$223.70
Purchase #2	$171.85	11.303%	$191.2742	$191.27	$191.25	$191.30
Purchase #3	$88.75	12.467%	$99.8145	$99.81	$99.80	$99.80
Purchase #4	$97.44	8.464%	$105.6873	$105.69	$105.70	$105.70
Purchase #5	$83.57	10.720%	$92.5287	$92.53	$92.55	$92.50
Purchase #6	$133.29	6.142%	$141.4767	$141.48	$141.50	$141.50
Purchase #7	$97.48	6.180%	$103.5043	$103.50	$103.50	$103.50
7 purchase totals =	$877.90		$958.0250	$958.02	$958.05	$958.00