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	$234.83	13.186%	$265.7947	$265.79	$265.80	$265.80
Purchase #2	$171.73	10.508%	$189.7754	$189.78	$189.80	$189.80
Purchase #3	$136.33	3.757%	$141.4519	$141.45	$141.45	$141.50
Purchase #4	$54.48	13.187%	$61.6643	$61.66	$61.65	$61.70
Purchase #5	$227.35	6.366%	$241.8231	$241.82	$241.80	$241.80
Purchase #6	$145.51	7.607%	$156.5789	$156.58	$156.60	$156.60
Purchase #7	$84.59	13.382%	$95.9098	$95.91	$95.90	$95.90
7 purchase totals =	$1,054.82		$1,152.9981	$1,152.99	$1,153.00	$1,153.10