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	$199.85	4.410%	$208.6634	$208.66	$208.65	$208.70
Purchase #2	$155.95	10.526%	$172.3653	$172.37	$172.35	$172.40
Purchase #3	$215.62	3.550%	$223.2745	$223.27	$223.25	$223.30
Purchase #4	$25.45	4.383%	$26.5655	$26.57	$26.55	$26.60
Purchase #5	$237.41	10.483%	$262.2977	$262.30	$262.30	$262.30
Purchase #6	$96.82	13.336%	$109.7319	$109.73	$109.75	$109.70
Purchase #7	$80.74	12.230%	$90.6145	$90.61	$90.60	$90.60
7 purchase totals =	$1,011.84		$1,093.5128	$1,093.51	$1,093.45	$1,093.60