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	$117.27	9.386%	$128.277	$128.28	$128.30	$128.30
Purchase #2	$115.33	9.270%	$126.0211	$126.02	$126.00	$126.00
Purchase #3	$96.43	4.564%	$100.8311	$100.83	$100.85	$100.80
Purchase #4	$159.56	7.437%	$171.4265	$171.43	$171.45	$171.40
Purchase #5	$9.47	13.512%	$10.7496	$10.75	$10.75	$10.70
Purchase #6	$103.27	9.492%	$113.0724	$113.07	$113.05	$113.10
Purchase #7	$127.60	3.432%	$131.9792	$131.98	$132.00	$132.00
7 purchase totals =	$728.93		$782.3569	$782.36	$782.40	$782.30