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	$78.93	6.183%	$83.8102	$83.81	$83.80	$83.80
Purchase #2	$13.87	10.638%	$15.3455	$15.35	$15.35	$15.30
Purchase #3	$196.92	9.809%	$216.2359	$216.24	$216.25	$216.20
Purchase #4	$152.47	9.544%	$167.0217	$167.02	$167.00	$167.00
Purchase #5	$159.66	6.170%	$169.511	$169.51	$169.50	$169.50
Purchase #6	$90.40	5.402%	$95.2834	$95.28	$95.30	$95.30
Purchase #7	$249.29	8.635%	$270.8162	$270.82	$270.80	$270.80
7 purchase totals =	$941.54		$1,018.0239	$1,018.03	$1,018.00	$1,017.90