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	$189.64	10.650%	$209.8367	$209.84	$209.85	$209.80
Purchase #2	$105.46	10.225%	$116.2433	$116.24	$116.25	$116.20
Purchase #3	$214.36	3.526%	$221.9183	$221.92	$221.90	$221.90
Purchase #4	$240.61	9.209%	$262.7678	$262.77	$262.75	$262.80
Purchase #5	$79.92	12.315%	$89.7621	$89.76	$89.75	$89.80
Purchase #6	$196.40	13.164%	$222.2541	$222.25	$222.25	$222.30
Purchase #7	$5.52	3.254%	$5.6996	$5.70	$5.70	$5.70
7 purchase totals =	$1,031.91		$1,128.4819	$1,128.48	$1,128.45	$1,128.50