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	$99.27	4.703%	$103.9387	$103.94	$103.95	$103.90
Purchase #2	$159.71	3.865%	$165.8828	$165.88	$165.90	$165.90
Purchase #3	$150.76	11.734%	$168.4502	$168.45	$168.45	$168.50
Purchase #4	$49.55	11.585%	$55.2904	$55.29	$55.30	$55.30
Purchase #5	$196.64	3.265%	$203.0603	$203.06	$203.05	$203.10
Purchase #6	$74.34	3.811%	$77.1731	$77.17	$77.15	$77.20
Purchase #7	$138.43	12.225%	$155.3531	$155.35	$155.35	$155.40
7 purchase totals =	$868.70		$929.1486	$929.14	$929.15	$929.30