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	$191.39	9.674%	$209.9051	$209.91	$209.90	$209.90
Purchase #2	$164.65	13.402%	$186.7164	$186.72	$186.70	$186.70
Purchase #3	$170.46	9.771%	$187.1156	$187.12	$187.10	$187.10
Purchase #4	$57.66	6.742%	$61.5474	$61.55	$61.55	$61.50
Purchase #5	$160.25	3.181%	$165.3476	$165.35	$165.35	$165.30
Purchase #6	$55.81	6.780%	$59.5939	$59.59	$59.60	$59.60
Purchase #7	$11.98	11.698%	$13.3814	$13.38	$13.40	$13.40
7 purchase totals =	$812.20		$883.6074	$883.62	$883.60	$883.50