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	$161.36	3.178%	$166.488	$166.49	$166.50	$166.50
Purchase #2	$229.47	3.253%	$236.9347	$236.93	$236.95	$236.90
Purchase #3	$8.86	6.481%	$9.4342	$9.43	$9.45	$9.40
Purchase #4	$75.57	12.599%	$85.0911	$85.09	$85.10	$85.10
Purchase #5	$65.46	10.598%	$72.3975	$72.40	$72.40	$72.40
Purchase #6	$131.59	12.689%	$148.2875	$148.29	$148.30	$148.30
Purchase #7	$33.89	13.301%	$38.3977	$38.40	$38.40	$38.40
7 purchase totals =	$706.20		$757.0307	$757.03	$757.10	$757.00