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	$81.47	4.197%	$84.8893	$84.89	$84.90	$84.90
Purchase #2	$222.74	5.716%	$235.4718	$235.47	$235.45	$235.50
Purchase #3	$84.71	6.298%	$90.045	$90.05	$90.05	$90.00
Purchase #4	$241.43	9.534%	$264.4479	$264.45	$264.45	$264.40
Purchase #5	$63.73	3.478%	$65.9465	$65.95	$65.95	$65.90
Purchase #6	$81.93	9.143%	$89.4209	$89.42	$89.40	$89.40
Purchase #7	$176.99	3.130%	$182.5298	$182.53	$182.55	$182.50
7 purchase totals =	$953.00		$1,012.7512	$1,012.76	$1,012.75	$1,012.60