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	$96.86	12.838%	$109.2949	$109.29	$109.30	$109.30
Purchase #2	$188.93	11.240%	$210.1657	$210.17	$210.15	$210.20
Purchase #3	$168.54	3.755%	$174.8687	$174.87	$174.85	$174.90
Purchase #4	$40.66	12.606%	$45.7856	$45.79	$45.80	$45.80
Purchase #5	$51.43	4.658%	$53.8256	$53.83	$53.85	$53.80
Purchase #6	$68.82	4.624%	$72.0022	$72.00	$72.00	$72.00
Purchase #7	$12.51	5.463%	$13.1934	$13.19	$13.20	$13.20
7 purchase totals =	$627.75		$679.1361	$679.14	$679.15	$679.20