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	$243.83	5.775%	$257.9112	$257.91	$257.90	$257.90
Purchase #2	$58.55	12.611%	$65.9337	$65.93	$65.95	$65.90
Purchase #3	$107.82	7.189%	$115.5712	$115.57	$115.55	$115.60
Purchase #4	$119.65	6.412%	$127.322	$127.32	$127.30	$127.30
Purchase #5	$165.81	3.707%	$171.9566	$171.96	$171.95	$172.00
Purchase #6	$71.96	13.201%	$81.4594	$81.46	$81.45	$81.50
Purchase #7	$247.70	3.707%	$256.8822	$256.88	$256.90	$256.90
7 purchase totals =	$1,015.32		$1,077.0363	$1,077.03	$1,077.00	$1,077.10