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	$221.75	7.493%	$238.3657	$238.37	$238.35	$238.40
Purchase #2	$243.34	11.697%	$271.8035	$271.80	$271.80	$271.80
Purchase #3	$29.63	13.261%	$33.5592	$33.56	$33.55	$33.60
Purchase #4	$52.76	7.340%	$56.6326	$56.63	$56.65	$56.60
Purchase #5	$81.83	6.247%	$86.9419	$86.94	$86.95	$86.90
Purchase #6	$176.77	8.118%	$191.1202	$191.12	$191.10	$191.10
Purchase #7	$88.70	13.253%	$100.4554	$100.46	$100.45	$100.50
7 purchase totals =	$894.78		$978.8785	$978.88	$978.85	$978.90