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	$217.96	9.483%	$238.6291	$238.63	$238.65	$238.60
Purchase #2	$80.89	6.226%	$85.9262	$85.93	$85.95	$85.90
Purchase #3	$200.87	13.217%	$227.419	$227.42	$227.40	$227.40
Purchase #4	$164.46	8.796%	$178.9259	$178.93	$178.95	$178.90
Purchase #5	$7.55	4.802%	$7.9126	$7.91	$7.90	$7.90
Purchase #6	$176.52	6.393%	$187.8049	$187.80	$187.80	$187.80
Purchase #7	$105.69	13.692%	$120.1611	$120.16	$120.15	$120.20
7 purchase totals =	$953.94		$1,046.7788	$1,046.78	$1,046.80	$1,046.70