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	$117.68	10.582%	$130.1329	$130.13	$130.15	$130.10
Purchase #2	$191.82	11.833%	$214.5181	$214.52	$214.50	$214.50
Purchase #3	$25.86	4.139%	$26.9303	$26.93	$26.95	$26.90
Purchase #4	$73.30	7.217%	$78.5901	$78.59	$78.60	$78.60
Purchase #5	$74.49	7.792%	$80.2943	$80.29	$80.30	$80.30
Purchase #6	$196.76	9.540%	$215.5309	$215.53	$215.55	$215.50
Purchase #7	$239.39	8.558%	$259.877	$259.88	$259.90	$259.90
7 purchase totals =	$919.30		$1,005.8736	$1,005.87	$1,005.95	$1,005.80