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	$102.83	8.351%	$111.4173	$111.42	$111.40	$111.40
Purchase #2	$111.87	5.728%	$118.2779	$118.28	$118.30	$118.30
Purchase #3	$41.28	4.121%	$42.9811	$42.98	$43.00	$43.00
Purchase #4	$76.36	9.129%	$83.3309	$83.33	$83.35	$83.30
Purchase #5	$207.91	7.219%	$222.919	$222.92	$222.90	$222.90
Purchase #6	$85.73	7.348%	$92.0294	$92.03	$92.05	$92.00
Purchase #7	$202.55	12.111%	$227.0808	$227.08	$227.10	$227.10
7 purchase totals =	$828.53		$898.0364	$898.04	$898.10	$898.00