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	$60.68	11.314%	$67.5453	$67.55	$67.55	$67.50
Purchase #2	$244.86	8.128%	$264.7622	$264.76	$264.75	$264.80
Purchase #3	$100.73	8.848%	$109.6426	$109.64	$109.65	$109.60
Purchase #4	$96.66	4.303%	$100.8193	$100.82	$100.80	$100.80
Purchase #5	$72.38	12.450%	$81.3913	$81.39	$81.40	$81.40
Purchase #6	$23.96	5.195%	$25.2047	$25.20	$25.20	$25.20
Purchase #7	$249.97	11.761%	$279.369	$279.37	$279.35	$279.40
7 purchase totals =	$849.24		$928.7344	$928.73	$928.70	$928.70