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	$153.74	11.511%	$171.437	$171.44	$171.45	$171.40
Purchase #2	$224.28	13.193%	$253.8693	$253.87	$253.85	$253.90
Purchase #3	$108.59	13.684%	$123.4495	$123.45	$123.45	$123.40
Purchase #4	$174.91	4.497%	$182.7757	$182.78	$182.80	$182.80
Purchase #5	$186.40	5.365%	$196.4004	$196.40	$196.40	$196.40
Purchase #6	$119.89	10.430%	$132.3945	$132.39	$132.40	$132.40
Purchase #7	$78.81	8.112%	$85.2031	$85.20	$85.20	$85.20
7 purchase totals =	$1,046.62		$1,145.5295	$1,145.53	$1,145.55	$1,145.50