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	$248.40	10.662%	$274.8844	$274.88	$274.90	$274.90
Purchase #2	$140.71	6.105%	$149.3003	$149.30	$149.30	$149.30
Purchase #3	$144.34	5.681%	$152.54	$152.54	$152.55	$152.50
Purchase #4	$213.67	11.124%	$237.4387	$237.44	$237.45	$237.40
Purchase #5	$111.28	11.156%	$123.6944	$123.69	$123.70	$123.70
Purchase #6	$102.65	10.584%	$113.5145	$113.51	$113.50	$113.50
Purchase #7	$148.56	13.384%	$168.4433	$168.44	$168.45	$168.40
7 purchase totals =	$1,109.61		$1,219.8156	$1,219.80	$1,219.85	$1,219.70