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	$169.77	9.166%	$185.3311	$185.33	$185.35	$185.30
Purchase #2	$214.97	13.874%	$244.7949	$244.79	$244.80	$244.80
Purchase #3	$235.65	7.316%	$252.8902	$252.89	$252.90	$252.90
Purchase #4	$71.74	12.476%	$80.6903	$80.69	$80.70	$80.70
Purchase #5	$63.74	12.421%	$71.6571	$71.66	$71.65	$71.70
Purchase #6	$196.58	13.372%	$222.8667	$222.87	$222.85	$222.90
Purchase #7	$82.81	4.651%	$86.6615	$86.66	$86.65	$86.70
7 purchase totals =	$1,035.26		$1,144.8918	$1,144.89	$1,144.90	$1,145.00