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	$177.78	4.833%	$186.3721	$186.37	$186.35	$186.40
Purchase #2	$110.32	12.276%	$123.8629	$123.86	$123.85	$123.90
Purchase #3	$25.89	7.734%	$27.8923	$27.89	$27.90	$27.90
Purchase #4	$249.82	10.118%	$275.0968	$275.10	$275.10	$275.10
Purchase #5	$182.59	13.184%	$206.6627	$206.66	$206.65	$206.70
Purchase #6	$140.45	8.139%	$151.8812	$151.88	$151.90	$151.90
Purchase #7	$232.90	3.626%	$241.345	$241.35	$241.35	$241.30
7 purchase totals =	$1,119.75		$1,213.1130	$1,213.11	$1,213.10	$1,213.20