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	$129.28	10.305%	$142.6023	$142.60	$142.60	$142.60
Purchase #2	$224.38	11.241%	$249.6026	$249.60	$249.60	$249.60
Purchase #3	$169.56	11.700%	$189.3985	$189.40	$189.40	$189.40
Purchase #4	$36.91	7.746%	$39.769	$39.77	$39.75	$39.80
Purchase #5	$81.75	4.579%	$85.4933	$85.49	$85.50	$85.50
Purchase #6	$140.89	10.224%	$155.2946	$155.29	$155.30	$155.30
Purchase #7	$10.94	4.779%	$11.4628	$11.46	$11.45	$11.50
7 purchase totals =	$793.71		$873.6231	$873.61	$873.60	$873.70