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	$143.95	8.754%	$156.5514	$156.55	$156.55	$156.60
Purchase #2	$220.44	3.376%	$227.8821	$227.88	$227.90	$227.90
Purchase #3	$224.29	10.287%	$247.3627	$247.36	$247.35	$247.40
Purchase #4	$62.53	4.645%	$65.4345	$65.43	$65.45	$65.40
Purchase #5	$152.63	12.192%	$171.2386	$171.24	$171.25	$171.20
Purchase #6	$69.89	3.771%	$72.5256	$72.53	$72.55	$72.50
Purchase #7	$148.49	9.294%	$162.2907	$162.29	$162.30	$162.30
7 purchase totals =	$1,022.22		$1,103.2856	$1,103.28	$1,103.35	$1,103.30