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	$91.95	3.859%	$95.4984	$95.50	$95.50	$95.50
Purchase #2	$151.48	11.536%	$168.9547	$168.95	$168.95	$169.00
Purchase #3	$103.40	9.356%	$113.0741	$113.07	$113.05	$113.10
Purchase #4	$55.61	4.692%	$58.2192	$58.22	$58.20	$58.20
Purchase #5	$146.40	3.380%	$151.3483	$151.35	$151.35	$151.30
Purchase #6	$45.98	9.287%	$50.2502	$50.25	$50.25	$50.30
Purchase #7	$171.70	7.477%	$184.538	$184.54	$184.55	$184.50
7 purchase totals =	$766.52		$821.8829	$821.88	$821.85	$821.90