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	$122.54	3.864%	$127.2749	$127.27	$127.25	$127.30
Purchase #2	$80.88	5.685%	$85.478	$85.48	$85.50	$85.50
Purchase #3	$232.31	11.865%	$259.8736	$259.87	$259.85	$259.90
Purchase #4	$190.78	12.768%	$215.1388	$215.14	$215.15	$215.10
Purchase #5	$181.86	10.169%	$200.3533	$200.35	$200.35	$200.40
Purchase #6	$193.67	8.138%	$209.4309	$209.43	$209.45	$209.40
Purchase #7	$103.69	8.796%	$112.8106	$112.81	$112.80	$112.80
7 purchase totals =	$1,105.73		$1,210.3601	$1,210.35	$1,210.35	$1,210.40