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	$235.32	6.737%	$251.1735	$251.17	$251.15	$251.20
Purchase #2	$28.90	8.560%	$31.3738	$31.37	$31.35	$31.40
Purchase #3	$83.37	7.324%	$89.476	$89.48	$89.50	$89.50
Purchase #4	$168.79	12.837%	$190.4576	$190.46	$190.45	$190.50
Purchase #5	$136.96	11.807%	$153.1309	$153.13	$153.15	$153.10
Purchase #6	$138.35	12.782%	$156.0339	$156.03	$156.05	$156.00
Purchase #7	$191.98	6.804%	$205.0423	$205.04	$205.05	$205.00
7 purchase totals =	$983.67		$1,076.6880	$1,076.68	$1,076.70	$1,076.70