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	$12.26	11.764%	$13.7023	$13.70	$13.70	$13.70
Purchase #2	$84.87	8.522%	$92.1026	$92.10	$92.10	$92.10
Purchase #3	$105.75	5.322%	$111.378	$111.38	$111.40	$111.40
Purchase #4	$104.53	13.851%	$119.0085	$119.01	$119.00	$119.00
Purchase #5	$201.43	10.606%	$222.7937	$222.79	$222.80	$222.80
Purchase #6	$110.82	11.402%	$123.4557	$123.46	$123.45	$123.50
Purchase #7	$233.29	13.874%	$265.6567	$265.66	$265.65	$265.70
7 purchase totals =	$852.95		$948.0975	$948.10	$948.10	$948.20