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	$105.70	6.809%	$112.8971	$112.90	$112.90	$112.90
Purchase #2	$52.83	12.152%	$59.2499	$59.25	$59.25	$59.20
Purchase #3	$110.98	4.421%	$115.8864	$115.89	$115.90	$115.90
Purchase #4	$26.49	4.475%	$27.6754	$27.68	$27.70	$27.70
Purchase #5	$103.38	9.221%	$112.9127	$112.91	$112.90	$112.90
Purchase #6	$143.38	5.237%	$150.8888	$150.89	$150.90	$150.90
Purchase #7	$154.91	9.627%	$169.8232	$169.82	$169.80	$169.80
7 purchase totals =	$697.67		$749.3335	$749.34	$749.35	$749.30