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	$213.43	6.790%	$227.9219	$227.92	$227.90	$227.90
Purchase #2	$173.50	7.269%	$186.1117	$186.11	$186.10	$186.10
Purchase #3	$136.96	6.273%	$145.5515	$145.55	$145.55	$145.60
Purchase #4	$154.33	9.374%	$168.7969	$168.80	$168.80	$168.80
Purchase #5	$83.55	7.654%	$89.9449	$89.94	$89.95	$89.90
Purchase #6	$42.57	3.159%	$43.9148	$43.91	$43.90	$43.90
Purchase #7	$169.86	10.811%	$188.2236	$188.22	$188.20	$188.20
7 purchase totals =	$974.20		$1,050.4653	$1,050.45	$1,050.40	$1,050.40