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	$181.93	5.164%	$191.3249	$191.32	$191.30	$191.30
Purchase #2	$37.63	8.633%	$40.8786	$40.88	$40.90	$40.90
Purchase #3	$222.81	11.420%	$248.2549	$248.25	$248.25	$248.30
Purchase #4	$12.26	3.208%	$12.6533	$12.65	$12.65	$12.70
Purchase #5	$56.69	8.449%	$61.4797	$61.48	$61.50	$61.50
Purchase #6	$102.34	3.147%	$105.5606	$105.56	$105.55	$105.60
Purchase #7	$43.66	9.283%	$47.713	$47.71	$47.70	$47.70
7 purchase totals =	$657.32		$707.8650	$707.85	$707.85	$708.00