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	$246.56	9.191%	$269.2213	$269.22	$269.20	$269.20
Purchase #2	$249.31	4.240%	$259.8807	$259.88	$259.90	$259.90
Purchase #3	$85.32	9.107%	$93.0901	$93.09	$93.10	$93.10
Purchase #4	$100.91	4.657%	$105.6094	$105.61	$105.60	$105.60
Purchase #5	$131.50	8.191%	$142.2712	$142.27	$142.25	$142.30
Purchase #6	$151.40	10.459%	$167.2349	$167.23	$167.25	$167.20
Purchase #7	$224.66	8.611%	$244.0055	$244.01	$244.00	$244.00
7 purchase totals =	$1,189.66		$1,281.3131	$1,281.31	$1,281.30	$1,281.30