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	$235.76	8.349%	$255.4436	$255.44	$255.45	$255.40
Purchase #2	$147.56	12.768%	$166.4005	$166.40	$166.40	$166.40
Purchase #3	$234.61	12.806%	$264.6542	$264.65	$264.65	$264.70
Purchase #4	$160.61	4.289%	$167.4986	$167.50	$167.50	$167.50
Purchase #5	$23.27	5.837%	$24.6283	$24.63	$24.65	$24.60
Purchase #6	$126.43	4.157%	$131.6857	$131.69	$131.70	$131.70
Purchase #7	$181.27	10.106%	$199.5891	$199.59	$199.60	$199.60
7 purchase totals =	$1,109.51		$1,209.9000	$1,209.90	$1,209.95	$1,209.90