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	$194.83	7.203%	$208.8636	$208.86	$208.85	$208.90
Purchase #2	$175.70	12.312%	$197.3322	$197.33	$197.35	$197.30
Purchase #3	$168.65	12.801%	$190.2389	$190.24	$190.25	$190.20
Purchase #4	$149.26	12.105%	$167.3279	$167.33	$167.35	$167.30
Purchase #5	$23.75	13.718%	$27.008	$27.01	$27.00	$27.00
Purchase #6	$85.73	4.773%	$89.8219	$89.82	$89.80	$89.80
Purchase #7	$168.85	7.665%	$181.7924	$181.79	$181.80	$181.80
7 purchase totals =	$966.77		$1,062.3849	$1,062.38	$1,062.40	$1,062.30