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	$51.49	12.553%	$57.9535	$57.95	$57.95	$58.00
Purchase #2	$86.52	4.843%	$90.7102	$90.71	$90.70	$90.70
Purchase #3	$43.28	3.709%	$44.8853	$44.89	$44.90	$44.90
Purchase #4	$240.82	5.637%	$254.395	$254.40	$254.40	$254.40
Purchase #5	$186.54	6.735%	$199.1035	$199.10	$199.10	$199.10
Purchase #6	$143.42	13.616%	$162.9481	$162.95	$162.95	$162.90
Purchase #7	$189.85	12.535%	$213.6477	$213.65	$213.65	$213.60
7 purchase totals =	$941.92		$1,023.6433	$1,023.65	$1,023.65	$1,023.60