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	$246.94	4.165%	$257.2251	$257.23	$257.25	$257.20
Purchase #2	$174.74	12.274%	$196.1876	$196.19	$196.20	$196.20
Purchase #3	$178.90	9.800%	$196.4322	$196.43	$196.45	$196.40
Purchase #4	$31.26	4.266%	$32.5936	$32.59	$32.60	$32.60
Purchase #5	$227.62	8.192%	$246.2666	$246.27	$246.25	$246.30
Purchase #6	$130.28	7.273%	$139.7553	$139.76	$139.75	$139.80
Purchase #7	$71.62	3.476%	$74.1095	$74.11	$74.10	$74.10
7 purchase totals =	$1,061.36		$1,142.5699	$1,142.58	$1,142.60	$1,142.60