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	$23.60	7.318%	$25.327	$25.33	$25.35	$25.30
Purchase #2	$96.62	6.219%	$102.6288	$102.63	$102.65	$102.60
Purchase #3	$178.99	6.346%	$190.3487	$190.35	$190.35	$190.30
Purchase #4	$105.52	8.492%	$114.4808	$114.48	$114.50	$114.50
Purchase #5	$65.90	10.537%	$72.8439	$72.84	$72.85	$72.80
Purchase #6	$211.25	10.719%	$233.8939	$233.89	$233.90	$233.90
Purchase #7	$239.63	9.595%	$262.6225	$262.62	$262.60	$262.60
7 purchase totals =	$921.51		$1,002.1456	$1,002.14	$1,002.20	$1,002.00