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	$55.60	11.259%	$61.86	$61.86	$61.85	$61.90
Purchase #2	$233.60	13.581%	$265.3252	$265.33	$265.35	$265.30
Purchase #3	$170.51	12.131%	$191.1946	$191.19	$191.20	$191.20
Purchase #4	$116.42	7.249%	$124.8593	$124.86	$124.85	$124.90
Purchase #5	$17.67	11.552%	$19.7112	$19.71	$19.70	$19.70
Purchase #6	$246.87	5.787%	$261.1564	$261.16	$261.15	$261.20
Purchase #7	$88.44	4.432%	$92.3597	$92.36	$92.35	$92.40
7 purchase totals =	$929.11		$1,016.4664	$1,016.47	$1,016.45	$1,016.60