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	$24.49	8.339%	$26.5322	$26.53	$26.55	$26.50
Purchase #2	$33.95	8.682%	$36.8975	$36.90	$36.90	$36.90
Purchase #3	$245.61	8.591%	$266.7104	$266.71	$266.70	$266.70
Purchase #4	$247.59	11.846%	$276.9195	$276.92	$276.90	$276.90
Purchase #5	$115.90	9.240%	$126.6092	$126.61	$126.60	$126.60
Purchase #6	$216.75	9.737%	$237.8549	$237.85	$237.85	$237.90
Purchase #7	$42.60	6.298%	$45.2829	$45.28	$45.30	$45.30
7 purchase totals =	$926.89		$1,016.8066	$1,016.80	$1,016.80	$1,016.80