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	$133.37	10.615%	$147.5272	$147.53	$147.55	$147.50
Purchase #2	$187.90	11.138%	$208.8283	$208.83	$208.85	$208.80
Purchase #3	$150.45	10.780%	$166.6685	$166.67	$166.65	$166.70
Purchase #4	$190.86	11.800%	$213.3815	$213.38	$213.40	$213.40
Purchase #5	$154.29	6.487%	$164.2988	$164.30	$164.30	$164.30
Purchase #6	$221.25	7.789%	$238.4832	$238.48	$238.50	$238.50
Purchase #7	$83.52	6.222%	$88.7166	$88.72	$88.70	$88.70
7 purchase totals =	$1,121.64		$1,227.9041	$1,227.91	$1,227.95	$1,227.90