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	$166.71	10.476%	$184.1745	$184.17	$184.15	$184.20
Purchase #2	$9.78	3.168%	$10.0898	$10.09	$10.10	$10.10
Purchase #3	$181.27	5.625%	$191.4664	$191.47	$191.45	$191.50
Purchase #4	$167.28	9.332%	$182.8906	$182.89	$182.90	$182.90
Purchase #5	$112.87	9.152%	$123.1999	$123.20	$123.20	$123.20
Purchase #6	$180.25	5.337%	$189.8699	$189.87	$189.85	$189.90
Purchase #7	$209.96	5.800%	$222.1377	$222.14	$222.15	$222.10
7 purchase totals =	$1,028.12		$1,103.8288	$1,103.83	$1,103.80	$1,103.90