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	$193.46	13.158%	$218.9155	$218.92	$218.90	$218.90
Purchase #2	$208.29	4.263%	$217.1694	$217.17	$217.15	$217.20
Purchase #3	$65.30	9.453%	$71.4728	$71.47	$71.45	$71.50
Purchase #4	$89.70	13.118%	$101.4668	$101.47	$101.45	$101.50
Purchase #5	$52.85	12.721%	$59.573	$59.57	$59.55	$59.60
Purchase #6	$227.29	7.516%	$244.3731	$244.37	$244.35	$244.40
Purchase #7	$174.87	12.179%	$196.1674	$196.17	$196.15	$196.20
7 purchase totals =	$1,011.76		$1,109.1380	$1,109.14	$1,109.00	$1,109.30