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	$139.58	12.145%	$156.532	$156.53	$156.55	$156.50
Purchase #2	$183.92	9.212%	$200.8627	$200.86	$200.85	$200.90
Purchase #3	$161.90	12.394%	$181.9659	$181.97	$181.95	$182.00
Purchase #4	$153.76	13.708%	$174.8374	$174.84	$174.85	$174.80
Purchase #5	$59.82	8.424%	$64.8592	$64.86	$64.85	$64.90
Purchase #6	$95.66	7.766%	$103.089	$103.09	$103.10	$103.10
Purchase #7	$180.47	4.462%	$188.5226	$188.52	$188.50	$188.50
7 purchase totals =	$975.11		$1,070.6688	$1,070.67	$1,070.65	$1,070.70