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	$130.99	13.307%	$148.4208	$148.42	$148.40	$148.40
Purchase #2	$116.27	6.550%	$123.8857	$123.89	$123.90	$123.90
Purchase #3	$95.76	8.731%	$104.1208	$104.12	$104.10	$104.10
Purchase #4	$113.89	10.610%	$125.9737	$125.97	$125.95	$126.00
Purchase #5	$193.70	8.321%	$209.8178	$209.82	$209.80	$209.80
Purchase #6	$213.75	5.197%	$224.8586	$224.86	$224.85	$224.90
Purchase #7	$76.63	7.222%	$82.1642	$82.16	$82.15	$82.20
7 purchase totals =	$940.99		$1,019.2416	$1,019.24	$1,019.15	$1,019.30