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	$232.30	10.517%	$256.731	$256.73	$256.75	$256.70
Purchase #2	$96.50	7.140%	$103.3901	$103.39	$103.40	$103.40
Purchase #3	$101.52	7.619%	$109.2548	$109.25	$109.25	$109.30
Purchase #4	$25.81	10.609%	$28.5482	$28.55	$28.55	$28.50
Purchase #5	$209.61	3.354%	$216.6403	$216.64	$216.65	$216.60
Purchase #6	$205.71	6.863%	$219.8279	$219.83	$219.85	$219.80
Purchase #7	$164.66	12.108%	$184.597	$184.60	$184.60	$184.60
7 purchase totals =	$1,036.11		$1,118.9893	$1,118.99	$1,119.05	$1,118.90