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	$177.37	10.631%	$196.2262	$196.23	$196.25	$196.20
Purchase #2	$147.39	3.237%	$152.161	$152.16	$152.15	$152.20
Purchase #3	$179.49	12.869%	$202.5886	$202.59	$202.60	$202.60
Purchase #4	$71.27	11.644%	$79.5687	$79.57	$79.55	$79.60
Purchase #5	$134.26	12.455%	$150.9821	$150.98	$151.00	$151.00
Purchase #6	$142.57	10.849%	$158.0374	$158.04	$158.05	$158.00
Purchase #7	$108.31	8.817%	$117.8597	$117.86	$117.85	$117.90
7 purchase totals =	$960.66		$1,057.4237	$1,057.43	$1,057.45	$1,057.50