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	$169.46	3.553%	$175.4809	$175.48	$175.50	$175.50
Purchase #2	$65.69	10.664%	$72.6952	$72.70	$72.70	$72.70
Purchase #3	$87.46	13.478%	$99.2479	$99.25	$99.25	$99.20
Purchase #4	$49.71	7.391%	$53.3841	$53.38	$53.40	$53.40
Purchase #5	$101.71	12.586%	$114.5112	$114.51	$114.50	$114.50
Purchase #6	$150.81	6.761%	$161.0063	$161.01	$161.00	$161.00
Purchase #7	$239.76	9.791%	$263.2349	$263.23	$263.25	$263.20
7 purchase totals =	$864.60		$939.5605	$939.56	$939.60	$939.50