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	$35.41	4.264%	$36.9199	$36.92	$36.90	$36.90
Purchase #2	$113.48	10.172%	$125.0232	$125.02	$125.00	$125.00
Purchase #3	$238.77	9.543%	$261.5558	$261.56	$261.55	$261.60
Purchase #4	$114.64	11.771%	$128.1343	$128.13	$128.15	$128.10
Purchase #5	$30.70	3.544%	$31.788	$31.79	$31.80	$31.80
Purchase #6	$249.80	12.515%	$281.0625	$281.06	$281.05	$281.10
Purchase #7	$186.27	5.554%	$196.6154	$196.62	$196.60	$196.60
7 purchase totals =	$969.07		$1,061.0991	$1,061.10	$1,061.05	$1,061.10