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	$125.25	7.688%	$134.8792	$134.88	$134.90	$134.90
Purchase #2	$102.30	6.102%	$108.5423	$108.54	$108.55	$108.50
Purchase #3	$189.52	13.463%	$215.0351	$215.04	$215.05	$215.00
Purchase #4	$177.59	10.788%	$196.7484	$196.75	$196.75	$196.70
Purchase #5	$132.30	6.644%	$141.09	$141.09	$141.10	$141.10
Purchase #6	$250.84	4.675%	$262.5668	$262.57	$262.55	$262.60
Purchase #7	$83.36	7.136%	$89.3086	$89.31	$89.30	$89.30
7 purchase totals =	$1,061.16		$1,148.1704	$1,148.18	$1,148.20	$1,148.10