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	$243.29	12.570%	$273.8716	$273.87	$273.85	$273.90
Purchase #2	$56.60	6.553%	$60.309	$60.31	$60.30	$60.30
Purchase #3	$63.73	13.360%	$72.2443	$72.24	$72.25	$72.20
Purchase #4	$149.86	3.332%	$154.8533	$154.85	$154.85	$154.90
Purchase #5	$239.95	13.846%	$273.1735	$273.17	$273.15	$273.20
Purchase #6	$246.94	3.213%	$254.8742	$254.87	$254.85	$254.90
Purchase #7	$9.95	3.874%	$10.3355	$10.34	$10.35	$10.30
7 purchase totals =	$1,010.32		$1,099.6614	$1,099.65	$1,099.60	$1,099.70