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	$214.40	9.489%	$234.7444	$234.74	$234.75	$234.70
Purchase #2	$140.29	11.596%	$156.558	$156.56	$156.55	$156.60
Purchase #3	$35.77	9.693%	$39.2372	$39.24	$39.25	$39.20
Purchase #4	$227.78	9.874%	$250.271	$250.27	$250.25	$250.30
Purchase #5	$189.55	12.720%	$213.6608	$213.66	$213.65	$213.70
Purchase #6	$74.61	7.612%	$80.2893	$80.29	$80.30	$80.30
Purchase #7	$142.85	7.150%	$153.0638	$153.06	$153.05	$153.10
7 purchase totals =	$1,025.25		$1,127.8245	$1,127.82	$1,127.80	$1,127.90