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	$227.94	6.288%	$242.2729	$242.27	$242.25	$242.30
Purchase #2	$101.37	3.160%	$104.5733	$104.57	$104.55	$104.60
Purchase #3	$112.69	10.564%	$124.5946	$124.59	$124.60	$124.60
Purchase #4	$139.31	6.148%	$147.8748	$147.87	$147.85	$147.90
Purchase #5	$119.83	5.357%	$126.2493	$126.25	$126.25	$126.20
Purchase #6	$50.59	9.564%	$55.4284	$55.43	$55.45	$55.40
Purchase #7	$113.61	9.421%	$124.3132	$124.31	$124.30	$124.30
7 purchase totals =	$865.34		$925.3065	$925.29	$925.25	$925.30