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	$112.62	13.315%	$127.6154	$127.62	$127.60	$127.60
Purchase #2	$147.95	13.528%	$167.9647	$167.96	$167.95	$168.00
Purchase #3	$17.72	4.648%	$18.5436	$18.54	$18.55	$18.50
Purchase #4	$9.80	13.448%	$11.1179	$11.12	$11.10	$11.10
Purchase #5	$74.88	6.140%	$79.4776	$79.48	$79.50	$79.50
Purchase #6	$134.34	5.397%	$141.5903	$141.59	$141.60	$141.60
Purchase #7	$103.91	11.433%	$115.79	$115.79	$115.80	$115.80
7 purchase totals =	$601.22		$662.0995	$662.10	$662.10	$662.10