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	$205.46	4.671%	$215.057	$215.06	$215.05	$215.10
Purchase #2	$196.41	10.255%	$216.5518	$216.55	$216.55	$216.60
Purchase #3	$20.79	13.846%	$23.6686	$23.67	$23.65	$23.70
Purchase #4	$66.59	8.760%	$72.4233	$72.42	$72.40	$72.40
Purchase #5	$42.57	4.339%	$44.4171	$44.42	$44.40	$44.40
Purchase #6	$9.48	13.840%	$10.792	$10.79	$10.80	$10.80
Purchase #7	$59.97	6.769%	$64.0294	$64.03	$64.05	$64.00
7 purchase totals =	$601.27		$646.9392	$646.94	$646.90	$647.00