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	$186.32	5.624%	$196.7986	$196.80	$196.80	$196.80
Purchase #2	$240.40	6.140%	$255.1606	$255.16	$255.15	$255.20
Purchase #3	$46.81	3.417%	$48.4095	$48.41	$48.40	$48.40
Purchase #4	$75.32	6.588%	$80.2821	$80.28	$80.30	$80.30
Purchase #5	$243.40	11.728%	$271.946	$271.95	$271.95	$271.90
Purchase #6	$215.90	11.566%	$240.871	$240.87	$240.85	$240.90
Purchase #7	$38.46	6.431%	$40.9334	$40.93	$40.95	$40.90
7 purchase totals =	$1,046.61		$1,134.4012	$1,134.40	$1,134.40	$1,134.40