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	$152.93	5.634%	$161.5461	$161.55	$161.55	$161.50
Purchase #2	$186.97	6.111%	$198.3957	$198.40	$198.40	$198.40
Purchase #3	$110.43	3.632%	$114.4408	$114.44	$114.45	$114.40
Purchase #4	$36.26	3.329%	$37.4671	$37.47	$37.45	$37.50
Purchase #5	$237.42	4.384%	$247.8285	$247.83	$247.85	$247.80
Purchase #6	$37.36	12.756%	$42.1256	$42.13	$42.15	$42.10
Purchase #7	$161.42	4.182%	$168.1706	$168.17	$168.15	$168.20
7 purchase totals =	$922.79		$969.9744	$969.99	$970.00	$969.90