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	$178.40	10.107%	$196.4309	$196.43	$196.45	$196.40
Purchase #2	$245.91	6.609%	$262.1622	$262.16	$262.15	$262.20
Purchase #3	$136.40	5.143%	$143.4151	$143.42	$143.40	$143.40
Purchase #4	$101.25	9.715%	$111.0864	$111.09	$111.10	$111.10
Purchase #5	$89.79	12.362%	$100.8898	$100.89	$100.90	$100.90
Purchase #6	$35.77	11.579%	$39.9118	$39.91	$39.90	$39.90
Purchase #7	$233.30	12.202%	$261.7673	$261.77	$261.75	$261.80
7 purchase totals =	$1,020.82		$1,115.6635	$1,115.67	$1,115.65	$1,115.70