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	$164.34	12.292%	$184.5407	$184.54	$184.55	$184.50
Purchase #2	$73.94	8.828%	$80.4674	$80.47	$80.45	$80.50
Purchase #3	$13.74	9.133%	$14.9949	$14.99	$15.00	$15.00
Purchase #4	$186.41	5.629%	$196.903	$196.90	$196.90	$196.90
Purchase #5	$184.98	6.158%	$196.3711	$196.37	$196.35	$196.40
Purchase #6	$244.47	7.714%	$263.3284	$263.33	$263.35	$263.30
Purchase #7	$135.82	9.854%	$149.2037	$149.20	$149.20	$149.20
7 purchase totals =	$1,003.70		$1,085.8092	$1,085.80	$1,085.80	$1,085.80