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	$66.83	12.635%	$75.274	$75.27	$75.25	$75.30
Purchase #2	$163.89	6.460%	$174.4773	$174.48	$174.50	$174.50
Purchase #3	$189.31	8.741%	$205.8576	$205.86	$205.85	$205.90
Purchase #4	$208.79	6.723%	$222.827	$222.83	$222.85	$222.80
Purchase #5	$95.36	5.308%	$100.4217	$100.42	$100.40	$100.40
Purchase #6	$172.67	13.304%	$195.642	$195.64	$195.65	$195.60
Purchase #7	$30.98	13.557%	$35.18	$35.18	$35.20	$35.20
7 purchase totals =	$927.83		$1,009.6796	$1,009.68	$1,009.70	$1,009.70