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	$211.42	4.273%	$220.454	$220.45	$220.45	$220.50
Purchase #2	$196.38	5.296%	$206.7803	$206.78	$206.80	$206.80
Purchase #3	$239.40	5.222%	$251.9015	$251.90	$251.90	$251.90
Purchase #4	$58.61	4.854%	$61.4549	$61.45	$61.45	$61.50
Purchase #5	$6.78	12.610%	$7.635	$7.64	$7.65	$7.60
Purchase #6	$121.62	3.522%	$125.9035	$125.90	$125.90	$125.90
Purchase #7	$114.98	11.777%	$128.5212	$128.52	$128.50	$128.50
7 purchase totals =	$949.19		$1,002.6504	$1,002.64	$1,002.65	$1,002.70