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	$237.68	10.356%	$262.2941	$262.29	$262.30	$262.30
Purchase #2	$90.49	12.242%	$101.5678	$101.57	$101.55	$101.60
Purchase #3	$56.37	8.456%	$61.1366	$61.14	$61.15	$61.10
Purchase #4	$226.80	5.763%	$239.8705	$239.87	$239.85	$239.90
Purchase #5	$95.82	5.293%	$100.8918	$100.89	$100.90	$100.90
Purchase #6	$58.28	4.802%	$61.0786	$61.08	$61.10	$61.10
Purchase #7	$208.70	7.297%	$223.9288	$223.93	$223.95	$223.90
7 purchase totals =	$974.14		$1,050.7682	$1,050.77	$1,050.80	$1,050.80