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	$14.75	5.145%	$15.5089	$15.51	$15.50	$15.50
Purchase #2	$108.91	9.432%	$119.1824	$119.18	$119.20	$119.20
Purchase #3	$219.60	8.657%	$238.6108	$238.61	$238.60	$238.60
Purchase #4	$63.69	6.647%	$67.9235	$67.92	$67.90	$67.90
Purchase #5	$229.77	4.108%	$239.209	$239.21	$239.20	$239.20
Purchase #6	$211.25	8.210%	$228.5936	$228.59	$228.60	$228.60
Purchase #7	$182.52	7.433%	$196.0867	$196.09	$196.10	$196.10
7 purchase totals =	$1,030.49		$1,105.1149	$1,105.11	$1,105.10	$1,105.10