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	$124.96	7.504%	$134.337	$134.34	$134.35	$134.30
Purchase #2	$50.32	6.233%	$53.4564	$53.46	$53.45	$53.50
Purchase #3	$165.84	9.542%	$181.6645	$181.66	$181.65	$181.70
Purchase #4	$35.86	11.296%	$39.9107	$39.91	$39.90	$39.90
Purchase #5	$101.32	13.735%	$115.2363	$115.24	$115.25	$115.20
Purchase #6	$72.72	7.260%	$77.9995	$78.00	$78.00	$78.00
Purchase #7	$68.68	5.303%	$72.3221	$72.32	$72.30	$72.30
7 purchase totals =	$619.70		$674.9265	$674.93	$674.90	$674.90