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	$148.93	4.262%	$155.2774	$155.28	$155.30	$155.30
Purchase #2	$232.73	11.635%	$259.8081	$259.81	$259.80	$259.80
Purchase #3	$191.83	6.505%	$204.3085	$204.31	$204.30	$204.30
Purchase #4	$138.89	8.600%	$150.8345	$150.83	$150.85	$150.80
Purchase #5	$14.65	3.718%	$15.1947	$15.19	$15.20	$15.20
Purchase #6	$176.59	13.696%	$200.7758	$200.78	$200.80	$200.80
Purchase #7	$165.85	5.314%	$174.6633	$174.66	$174.65	$174.70
7 purchase totals =	$1,069.47		$1,160.8623	$1,160.86	$1,160.90	$1,160.90