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	$200.54	11.575%	$223.7525	$223.75	$223.75	$223.80
Purchase #2	$227.46	6.560%	$242.3814	$242.38	$242.40	$242.40
Purchase #3	$186.48	12.201%	$209.2324	$209.23	$209.25	$209.20
Purchase #4	$62.58	6.185%	$66.4506	$66.45	$66.45	$66.50
Purchase #5	$80.91	4.494%	$84.5461	$84.55	$84.55	$84.50
Purchase #6	$54.59	5.432%	$57.5553	$57.56	$57.55	$57.60
Purchase #7	$209.93	5.348%	$221.1571	$221.16	$221.15	$221.20
7 purchase totals =	$1,022.49		$1,105.0754	$1,105.08	$1,105.10	$1,105.20