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	$165.38	4.436%	$172.7163	$172.72	$172.70	$172.70
Purchase #2	$200.80	6.107%	$213.0629	$213.06	$213.05	$213.10
Purchase #3	$67.65	8.346%	$73.2961	$73.30	$73.30	$73.30
Purchase #4	$55.38	7.138%	$59.333	$59.33	$59.35	$59.30
Purchase #5	$11.39	13.736%	$12.9545	$12.95	$12.95	$13.00
Purchase #6	$69.48	7.522%	$74.7063	$74.71	$74.70	$74.70
Purchase #7	$156.45	5.800%	$165.5241	$165.52	$165.50	$165.50
7 purchase totals =	$726.53		$771.5932	$771.59	$771.55	$771.60