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	$153.30	3.556%	$158.7513	$158.75	$158.75	$158.80
Purchase #2	$131.60	3.582%	$136.3139	$136.31	$136.30	$136.30
Purchase #3	$78.56	13.387%	$89.0768	$89.08	$89.10	$89.10
Purchase #4	$65.88	8.419%	$71.4264	$71.43	$71.45	$71.40
Purchase #5	$80.61	6.273%	$85.6667	$85.67	$85.65	$85.70
Purchase #6	$88.40	4.390%	$92.2808	$92.28	$92.30	$92.30
Purchase #7	$176.29	10.612%	$194.9979	$195.00	$195.00	$195.00
7 purchase totals =	$774.64		$828.5138	$828.52	$828.55	$828.60