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	$174.62	12.753%	$196.8893	$196.89	$196.90	$196.90
Purchase #2	$242.43	5.292%	$255.2594	$255.26	$255.25	$255.30
Purchase #3	$83.64	3.189%	$86.3073	$86.31	$86.30	$86.30
Purchase #4	$234.43	12.867%	$264.5941	$264.59	$264.60	$264.60
Purchase #5	$229.94	3.228%	$237.3625	$237.36	$237.35	$237.40
Purchase #6	$102.53	3.651%	$106.2734	$106.27	$106.25	$106.30
Purchase #7	$45.38	13.280%	$51.4065	$51.41	$51.40	$51.40
7 purchase totals =	$1,112.97		$1,198.0925	$1,198.09	$1,198.05	$1,198.20