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	$134.56	5.324%	$141.724	$141.72	$141.70	$141.70
Purchase #2	$98.81	10.354%	$109.0408	$109.04	$109.05	$109.00
Purchase #3	$191.85	11.198%	$213.3334	$213.33	$213.35	$213.30
Purchase #4	$35.68	9.388%	$39.0296	$39.03	$39.05	$39.00
Purchase #5	$160.58	6.497%	$171.0129	$171.01	$171.00	$171.00
Purchase #6	$86.53	10.816%	$95.8891	$95.89	$95.90	$95.90
Purchase #7	$243.58	12.870%	$274.9287	$274.93	$274.95	$274.90
7 purchase totals =	$951.59		$1,044.9585	$1,044.95	$1,045.00	$1,044.80