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	$211.85	13.836%	$241.1616	$241.16	$241.15	$241.20
Purchase #2	$176.73	7.562%	$190.0943	$190.09	$190.10	$190.10
Purchase #3	$27.81	13.541%	$31.5758	$31.58	$31.60	$31.60
Purchase #4	$179.41	13.694%	$203.9784	$203.98	$204.00	$204.00
Purchase #5	$102.41	7.134%	$109.7159	$109.72	$109.70	$109.70
Purchase #6	$130.65	10.360%	$144.1853	$144.19	$144.20	$144.20
Purchase #7	$71.66	13.488%	$81.3255	$81.33	$81.35	$81.30
7 purchase totals =	$900.52		$1,002.0368	$1,002.05	$1,002.10	$1,002.10