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	$116.98	8.218%	$126.5934	$126.59	$126.60	$126.60
Purchase #2	$39.39	3.560%	$40.7923	$40.79	$40.80	$40.80
Purchase #3	$53.56	11.359%	$59.6439	$59.64	$59.65	$59.60
Purchase #4	$245.99	3.837%	$255.4286	$255.43	$255.45	$255.40
Purchase #5	$201.48	4.466%	$210.4781	$210.48	$210.50	$210.50
Purchase #6	$74.33	3.591%	$76.9992	$77.00	$77.00	$77.00
Purchase #7	$216.50	6.829%	$231.2848	$231.28	$231.30	$231.30
7 purchase totals =	$948.23		$1,001.2203	$1,001.21	$1,001.30	$1,001.20