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	$197.57	13.817%	$224.8682	$224.87	$224.85	$224.90
Purchase #2	$67.31	4.261%	$70.1781	$70.18	$70.20	$70.20
Purchase #3	$57.39	3.493%	$59.3946	$59.39	$59.40	$59.40
Purchase #4	$97.80	8.350%	$105.9663	$105.97	$105.95	$106.00
Purchase #5	$187.54	4.736%	$196.4219	$196.42	$196.40	$196.40
Purchase #6	$203.90	11.602%	$227.5565	$227.56	$227.55	$227.60
Purchase #7	$128.45	11.260%	$142.9135	$142.91	$142.90	$142.90
7 purchase totals =	$939.96		$1,027.2991	$1,027.30	$1,027.25	$1,027.40