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	$134.46	13.265%	$152.2961	$152.30	$152.30	$152.30
Purchase #2	$16.91	7.241%	$18.1345	$18.13	$18.15	$18.10
Purchase #3	$120.33	9.320%	$131.5448	$131.54	$131.55	$131.50
Purchase #4	$169.95	3.155%	$175.3119	$175.31	$175.30	$175.30
Purchase #5	$24.54	10.425%	$27.0983	$27.10	$27.10	$27.10
Purchase #6	$190.71	5.383%	$200.9759	$200.98	$201.00	$201.00
Purchase #7	$47.67	9.499%	$52.1982	$52.20	$52.20	$52.20
7 purchase totals =	$704.57		$757.5597	$757.56	$757.60	$757.50