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	$146.71	10.689%	$162.3918	$162.39	$162.40	$162.40
Purchase #2	$215.34	4.634%	$225.3189	$225.32	$225.30	$225.30
Purchase #3	$196.82	13.225%	$222.8494	$222.85	$222.85	$222.80
Purchase #4	$115.31	4.393%	$120.3756	$120.38	$120.40	$120.40
Purchase #5	$66.28	13.673%	$75.3425	$75.34	$75.35	$75.30
Purchase #6	$47.62	4.780%	$49.8962	$49.90	$49.90	$49.90
Purchase #7	$152.90	12.158%	$171.4896	$171.49	$171.50	$171.50
7 purchase totals =	$940.98		$1,027.6640	$1,027.67	$1,027.70	$1,027.60