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	$117.69	8.185%	$127.3229	$127.32	$127.30	$127.30
Purchase #2	$215.79	5.655%	$227.9929	$227.99	$228.00	$228.00
Purchase #3	$50.85	12.683%	$57.2993	$57.30	$57.30	$57.30
Purchase #4	$92.60	10.639%	$102.4517	$102.45	$102.45	$102.50
Purchase #5	$71.64	6.565%	$76.3432	$76.34	$76.35	$76.30
Purchase #6	$212.79	4.681%	$222.7507	$222.75	$222.75	$222.80
Purchase #7	$161.53	11.271%	$179.736	$179.74	$179.75	$179.70
7 purchase totals =	$922.89		$993.8967	$993.89	$993.90	$993.90