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	$249.79	6.274%	$265.4618	$265.46	$265.45	$265.50
Purchase #2	$193.27	13.281%	$218.9382	$218.94	$218.95	$218.90
Purchase #3	$19.51	7.189%	$20.9126	$20.91	$20.90	$20.90
Purchase #4	$199.27	3.111%	$205.4693	$205.47	$205.45	$205.50
Purchase #5	$71.88	4.562%	$75.1592	$75.16	$75.15	$75.20
Purchase #6	$103.90	5.484%	$109.5979	$109.60	$109.60	$109.60
Purchase #7	$195.55	7.416%	$210.052	$210.05	$210.05	$210.10
7 purchase totals =	$1,033.17		$1,105.5910	$1,105.59	$1,105.55	$1,105.70