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	$76.93	10.515%	$85.0192	$85.02	$85.00	$85.00
Purchase #2	$32.56	5.556%	$34.369	$34.37	$34.35	$34.40
Purchase #3	$72.32	4.623%	$75.6634	$75.66	$75.65	$75.70
Purchase #4	$53.31	10.183%	$58.7386	$58.74	$58.75	$58.70
Purchase #5	$72.71	10.458%	$80.314	$80.31	$80.30	$80.30
Purchase #6	$61.41	9.217%	$67.0702	$67.07	$67.05	$67.10
Purchase #7	$59.77	13.407%	$67.7834	$67.78	$67.80	$67.80
7 purchase totals =	$429.01		$468.9578	$468.95	$468.90	$469.00