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	$65.85	9.472%	$72.0873	$72.09	$72.10	$72.10
Purchase #2	$8.87	11.790%	$9.9158	$9.92	$9.90	$9.90
Purchase #3	$192.40	9.839%	$211.3302	$211.33	$211.35	$211.30
Purchase #4	$83.68	7.398%	$89.8706	$89.87	$89.85	$89.90
Purchase #5	$232.34	10.836%	$257.5164	$257.52	$257.50	$257.50
Purchase #6	$64.98	11.608%	$72.5229	$72.52	$72.50	$72.50
Purchase #7	$107.84	3.411%	$111.5184	$111.52	$111.50	$111.50
7 purchase totals =	$755.96		$824.7616	$824.77	$824.70	$824.70