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	$247.33	11.426%	$275.5899	$275.59	$275.60	$275.60
Purchase #2	$216.33	9.702%	$237.3183	$237.32	$237.30	$237.30
Purchase #3	$74.64	5.623%	$78.837	$78.84	$78.85	$78.80
Purchase #4	$220.64	8.313%	$238.9818	$238.98	$239.00	$239.00
Purchase #5	$212.90	8.257%	$230.4792	$230.48	$230.50	$230.50
Purchase #6	$237.40	12.830%	$267.8584	$267.86	$267.85	$267.90
Purchase #7	$53.26	3.706%	$55.2338	$55.23	$55.25	$55.20
7 purchase totals =	$1,262.50		$1,384.2984	$1,384.30	$1,384.35	$1,384.30