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	$146.32	4.440%	$152.8166	$152.82	$152.80	$152.80
Purchase #2	$219.66	10.734%	$243.2383	$243.24	$243.25	$243.20
Purchase #3	$52.43	10.203%	$57.7794	$57.78	$57.80	$57.80
Purchase #4	$112.36	7.158%	$120.4027	$120.40	$120.40	$120.40
Purchase #5	$184.71	6.290%	$196.3283	$196.33	$196.35	$196.30
Purchase #6	$160.83	13.773%	$182.9811	$182.98	$183.00	$183.00
Purchase #7	$196.78	10.715%	$217.865	$217.87	$217.85	$217.90
7 purchase totals =	$1,073.09		$1,171.4114	$1,171.42	$1,171.45	$1,171.40