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	$239.51	9.320%	$261.8323	$261.83	$261.85	$261.80
Purchase #2	$6.86	11.400%	$7.642	$7.64	$7.65	$7.60
Purchase #3	$247.70	3.237%	$255.718	$255.72	$255.70	$255.70
Purchase #4	$238.56	7.404%	$256.223	$256.22	$256.20	$256.20
Purchase #5	$125.93	4.466%	$131.554	$131.55	$131.55	$131.60
Purchase #6	$110.76	5.259%	$116.5849	$116.58	$116.60	$116.60
Purchase #7	$18.55	10.398%	$20.4788	$20.48	$20.50	$20.50
7 purchase totals =	$987.87		$1,050.0330	$1,050.02	$1,050.05	$1,050.00