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	$192.38	3.583%	$199.273	$199.27	$199.25	$199.30
Purchase #2	$152.34	3.778%	$158.0954	$158.10	$158.10	$158.10
Purchase #3	$102.39	4.123%	$106.6115	$106.61	$106.60	$106.60
Purchase #4	$69.60	3.425%	$71.9838	$71.98	$72.00	$72.00
Purchase #5	$195.39	3.813%	$202.8402	$202.84	$202.85	$202.80
Purchase #6	$71.79	6.732%	$76.6229	$76.62	$76.60	$76.60
Purchase #7	$114.71	7.671%	$123.5094	$123.51	$123.50	$123.50
7 purchase totals =	$898.60		$938.9362	$938.93	$938.90	$938.90