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	$82.77	10.213%	$91.2233	$91.22	$91.20	$91.20
Purchase #2	$187.42	5.758%	$198.2116	$198.21	$198.20	$198.20
Purchase #3	$220.57	3.308%	$227.8665	$227.87	$227.85	$227.90
Purchase #4	$183.76	3.635%	$190.4397	$190.44	$190.45	$190.40
Purchase #5	$246.55	12.134%	$276.4664	$276.47	$276.45	$276.50
Purchase #6	$77.28	6.578%	$82.3635	$82.36	$82.35	$82.40
Purchase #7	$141.93	10.137%	$156.3174	$156.32	$156.30	$156.30
7 purchase totals =	$1,140.28		$1,222.8884	$1,222.89	$1,222.80	$1,222.90