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	$44.68	8.278%	$48.3786	$48.38	$48.40	$48.40
Purchase #2	$115.70	12.746%	$130.4471	$130.45	$130.45	$130.40
Purchase #3	$70.91	3.367%	$73.2975	$73.30	$73.30	$73.30
Purchase #4	$40.47	3.603%	$41.9281	$41.93	$41.95	$41.90
Purchase #5	$55.28	4.721%	$57.8898	$57.89	$57.90	$57.90
Purchase #6	$239.47	10.222%	$263.9486	$263.95	$263.95	$263.90
Purchase #7	$59.96	7.334%	$64.3575	$64.36	$64.35	$64.40
7 purchase totals =	$626.47		$680.2472	$680.26	$680.30	$680.20