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	$210.76	10.204%	$232.266	$232.27	$232.25	$232.30
Purchase #2	$127.72	10.301%	$140.8764	$140.88	$140.90	$140.90
Purchase #3	$166.78	3.263%	$172.222	$172.22	$172.20	$172.20
Purchase #4	$104.27	8.366%	$112.9932	$112.99	$113.00	$113.00
Purchase #5	$18.25	13.760%	$20.7612	$20.76	$20.75	$20.80
Purchase #6	$91.57	4.331%	$95.5359	$95.54	$95.55	$95.50
Purchase #7	$217.27	4.804%	$227.7077	$227.71	$227.70	$227.70
7 purchase totals =	$936.62		$1,002.3624	$1,002.37	$1,002.35	$1,002.40