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	$85.80	10.162%	$94.519	$94.52	$94.50	$94.50
Purchase #2	$171.81	12.341%	$193.0131	$193.01	$193.00	$193.00
Purchase #3	$26.96	5.522%	$28.4487	$28.45	$28.45	$28.40
Purchase #4	$128.76	6.534%	$137.1732	$137.17	$137.15	$137.20
Purchase #5	$27.39	6.818%	$29.2575	$29.26	$29.25	$29.30
Purchase #6	$235.83	8.475%	$255.8166	$255.82	$255.80	$255.80
Purchase #7	$56.89	3.715%	$59.0035	$59.00	$59.00	$59.00
7 purchase totals =	$733.44		$797.2316	$797.23	$797.15	$797.20