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	$31.93	8.590%	$34.6728	$34.67	$34.65	$34.70
Purchase #2	$170.33	12.295%	$191.2721	$191.27	$191.25	$191.30
Purchase #3	$156.29	8.177%	$169.0698	$169.07	$169.05	$169.10
Purchase #4	$101.85	7.581%	$109.5712	$109.57	$109.55	$109.60
Purchase #5	$86.73	3.621%	$89.8705	$89.87	$89.85	$89.90
Purchase #6	$250.45	6.348%	$266.3486	$266.35	$266.35	$266.30
Purchase #7	$77.29	4.164%	$80.5084	$80.51	$80.50	$80.50
7 purchase totals =	$874.87		$941.3134	$941.31	$941.20	$941.40