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	$101.28	10.452%	$111.8658	$111.87	$111.85	$111.90
Purchase #2	$218.95	10.791%	$242.5769	$242.58	$242.60	$242.60
Purchase #3	$81.88	9.789%	$89.8952	$89.90	$89.90	$89.90
Purchase #4	$196.49	8.179%	$212.5609	$212.56	$212.55	$212.60
Purchase #5	$198.75	4.172%	$207.0419	$207.04	$207.05	$207.00
Purchase #6	$148.82	8.505%	$161.4771	$161.48	$161.50	$161.50
Purchase #7	$145.91	5.323%	$153.6768	$153.68	$153.70	$153.70
7 purchase totals =	$1,092.08		$1,179.0946	$1,179.11	$1,179.15	$1,179.20