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	$248.63	7.654%	$267.6601	$267.66	$267.65	$267.70
Purchase #2	$85.77	13.698%	$97.5188	$97.52	$97.50	$97.50
Purchase #3	$51.66	10.850%	$57.2651	$57.27	$57.25	$57.30
Purchase #4	$143.34	4.546%	$149.8562	$149.86	$149.85	$149.90
Purchase #5	$147.45	11.446%	$164.3271	$164.33	$164.35	$164.30
Purchase #6	$93.94	11.852%	$105.0738	$105.07	$105.05	$105.10
Purchase #7	$109.29	13.314%	$123.8409	$123.84	$123.85	$123.80
7 purchase totals =	$880.08		$965.5420	$965.55	$965.50	$965.60