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	$111.84	6.691%	$119.3232	$119.32	$119.30	$119.30
Purchase #2	$52.87	5.812%	$55.9428	$55.94	$55.95	$55.90
Purchase #3	$233.64	6.631%	$249.1327	$249.13	$249.15	$249.10
Purchase #4	$208.40	13.473%	$236.4777	$236.48	$236.50	$236.50
Purchase #5	$145.31	9.479%	$159.0839	$159.08	$159.10	$159.10
Purchase #6	$171.55	5.131%	$180.3522	$180.35	$180.35	$180.40
Purchase #7	$92.64	11.527%	$103.3186	$103.32	$103.30	$103.30
7 purchase totals =	$1,016.25		$1,103.6311	$1,103.62	$1,103.65	$1,103.60