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	$59.71	4.663%	$62.4943	$62.49	$62.50	$62.50
Purchase #2	$43.55	8.813%	$47.3881	$47.39	$47.40	$47.40
Purchase #3	$192.32	12.625%	$216.6004	$216.60	$216.60	$216.60
Purchase #4	$151.50	6.199%	$160.8915	$160.89	$160.90	$160.90
Purchase #5	$144.91	11.106%	$161.0037	$161.00	$161.00	$161.00
Purchase #6	$174.64	10.541%	$193.0488	$193.05	$193.05	$193.00
Purchase #7	$212.73	4.573%	$222.4581	$222.46	$222.45	$222.50
7 purchase totals =	$979.36		$1,063.8849	$1,063.88	$1,063.90	$1,063.90