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	$42.68	9.764%	$46.8473	$46.85	$46.85	$46.80
Purchase #2	$217.33	9.661%	$238.3263	$238.33	$238.35	$238.30
Purchase #3	$153.92	9.668%	$168.801	$168.80	$168.80	$168.80
Purchase #4	$51.58	12.333%	$57.9414	$57.94	$57.95	$57.90
Purchase #5	$25.28	12.532%	$28.4481	$28.45	$28.45	$28.40
Purchase #6	$77.59	7.605%	$83.4907	$83.49	$83.50	$83.50
Purchase #7	$98.54	13.355%	$111.7	$111.70	$111.70	$111.70
7 purchase totals =	$666.92		$735.5548	$735.56	$735.60	$735.40