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	$208.47	4.631%	$218.1242	$218.12	$218.10	$218.10
Purchase #2	$237.45	11.781%	$265.424	$265.42	$265.40	$265.40
Purchase #3	$76.30	4.115%	$79.4397	$79.44	$79.45	$79.40
Purchase #4	$95.46	3.589%	$98.8861	$98.89	$98.90	$98.90
Purchase #5	$33.82	12.264%	$37.9677	$37.97	$37.95	$38.00
Purchase #6	$213.69	5.695%	$225.8596	$225.86	$225.85	$225.90
Purchase #7	$89.32	11.326%	$99.4364	$99.44	$99.45	$99.40
7 purchase totals =	$954.51		$1,025.1377	$1,025.14	$1,025.10	$1,025.10