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	$142.45	4.158%	$148.3731	$148.37	$148.35	$148.40
Purchase #2	$85.72	5.369%	$90.3223	$90.32	$90.30	$90.30
Purchase #3	$90.61	8.121%	$97.9684	$97.97	$97.95	$98.00
Purchase #4	$18.83	7.179%	$20.1818	$20.18	$20.20	$20.20
Purchase #5	$108.58	6.392%	$115.5204	$115.52	$115.50	$115.50
Purchase #6	$35.63	5.340%	$37.5326	$37.53	$37.55	$37.50
Purchase #7	$125.63	11.383%	$139.9305	$139.93	$139.95	$139.90
7 purchase totals =	$607.45		$649.8291	$649.82	$649.80	$649.80