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	$139.39	6.846%	$148.9326	$148.93	$148.95	$148.90
Purchase #2	$80.50	11.177%	$89.4975	$89.50	$89.50	$89.50
Purchase #3	$104.71	8.215%	$113.3119	$113.31	$113.30	$113.30
Purchase #4	$66.25	6.276%	$70.4079	$70.41	$70.40	$70.40
Purchase #5	$205.44	6.289%	$218.3601	$218.36	$218.35	$218.40
Purchase #6	$234.34	9.514%	$256.6351	$256.64	$256.65	$256.60
Purchase #7	$233.88	10.776%	$259.0829	$259.08	$259.10	$259.10
7 purchase totals =	$1,064.51		$1,156.2280	$1,156.23	$1,156.25	$1,156.20