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	$238.56	8.529%	$258.9068	$258.91	$258.90	$258.90
Purchase #2	$33.58	12.661%	$37.8316	$37.83	$37.85	$37.80
Purchase #3	$48.75	10.819%	$54.0243	$54.02	$54.00	$54.00
Purchase #4	$45.75	11.133%	$50.8433	$50.84	$50.85	$50.80
Purchase #5	$19.32	6.425%	$20.5613	$20.56	$20.55	$20.60
Purchase #6	$196.61	7.463%	$211.283	$211.28	$211.30	$211.30
Purchase #7	$125.41	9.743%	$137.6287	$137.63	$137.65	$137.60
7 purchase totals =	$707.98		$771.0790	$771.07	$771.10	$771.00