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	$186.42	11.628%	$208.0969	$208.10	$208.10	$208.10
Purchase #2	$29.82	9.112%	$32.5372	$32.54	$32.55	$32.50
Purchase #3	$218.67	12.602%	$246.2268	$246.23	$246.25	$246.20
Purchase #4	$30.92	7.640%	$33.2823	$33.28	$33.30	$33.30
Purchase #5	$125.51	6.870%	$134.1325	$134.13	$134.15	$134.10
Purchase #6	$38.39	12.372%	$43.1396	$43.14	$43.15	$43.10
Purchase #7	$7.25	7.824%	$7.8172	$7.82	$7.80	$7.80
7 purchase totals =	$636.98		$705.2325	$705.24	$705.30	$705.10