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	$33.76	10.776%	$37.398	$37.40	$37.40	$37.40
Purchase #2	$206.52	3.469%	$213.6842	$213.68	$213.70	$213.70
Purchase #3	$116.76	11.609%	$130.3147	$130.31	$130.30	$130.30
Purchase #4	$86.94	7.483%	$93.4457	$93.45	$93.45	$93.40
Purchase #5	$142.65	13.272%	$161.5825	$161.58	$161.60	$161.60
Purchase #6	$227.94	13.619%	$258.9831	$258.98	$259.00	$259.00
Purchase #7	$246.97	3.377%	$255.3102	$255.31	$255.30	$255.30
7 purchase totals =	$1,061.54		$1,150.7184	$1,150.71	$1,150.75	$1,150.70