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	$83.72	10.615%	$92.6069	$92.61	$92.60	$92.60
Purchase #2	$167.51	13.180%	$189.5878	$189.59	$189.60	$189.60
Purchase #3	$122.50	11.671%	$136.797	$136.80	$136.80	$136.80
Purchase #4	$71.38	10.318%	$78.745	$78.75	$78.75	$78.70
Purchase #5	$98.36	3.802%	$102.0996	$102.10	$102.10	$102.10
Purchase #6	$179.54	3.499%	$185.8221	$185.82	$185.80	$185.80
Purchase #7	$113.77	8.301%	$123.214	$123.21	$123.20	$123.20
7 purchase totals =	$836.78		$908.8724	$908.88	$908.85	$908.80