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	$112.97	8.252%	$122.2923	$122.29	$122.30	$122.30
Purchase #2	$231.97	3.479%	$240.0402	$240.04	$240.05	$240.00
Purchase #3	$164.76	10.620%	$182.2575	$182.26	$182.25	$182.30
Purchase #4	$37.30	5.316%	$39.2829	$39.28	$39.30	$39.30
Purchase #5	$66.53	8.748%	$72.35	$72.35	$72.35	$72.40
Purchase #6	$81.63	4.690%	$85.4584	$85.46	$85.45	$85.50
Purchase #7	$250.64	9.743%	$275.0599	$275.06	$275.05	$275.10
7 purchase totals =	$945.80		$1,016.7412	$1,016.74	$1,016.75	$1,016.90