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	$155.63	13.173%	$176.1311	$176.13	$176.15	$176.10
Purchase #2	$221.34	7.571%	$238.0977	$238.10	$238.10	$238.10
Purchase #3	$12.55	12.834%	$14.1607	$14.16	$14.15	$14.20
Purchase #4	$225.48	3.385%	$233.1125	$233.11	$233.10	$233.10
Purchase #5	$141.35	6.601%	$150.6805	$150.68	$150.70	$150.70
Purchase #6	$48.92	7.155%	$52.4202	$52.42	$52.40	$52.40
Purchase #7	$100.30	13.542%	$113.8826	$113.88	$113.90	$113.90
7 purchase totals =	$905.57		$978.4853	$978.48	$978.50	$978.50