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	$128.39	3.333%	$132.6692	$132.67	$132.65	$132.70
Purchase #2	$211.73	5.198%	$222.7357	$222.74	$222.75	$222.70
Purchase #3	$51.27	7.709%	$55.2224	$55.22	$55.20	$55.20
Purchase #4	$95.85	13.430%	$108.7227	$108.72	$108.70	$108.70
Purchase #5	$24.27	6.515%	$25.8512	$25.85	$25.85	$25.90
Purchase #6	$38.90	7.711%	$41.8996	$41.90	$41.90	$41.90
Purchase #7	$88.65	6.224%	$94.1676	$94.17	$94.15	$94.20
7 purchase totals =	$639.06		$681.2684	$681.27	$681.20	$681.30