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	$10.89	4.640%	$11.3953	$11.40	$11.40	$11.40
Purchase #2	$94.80	3.250%	$97.881	$97.88	$97.90	$97.90
Purchase #3	$163.39	3.537%	$169.1691	$169.17	$169.15	$169.20
Purchase #4	$56.96	9.145%	$62.169	$62.17	$62.15	$62.20
Purchase #5	$91.50	8.827%	$99.5767	$99.58	$99.60	$99.60
Purchase #6	$98.72	3.484%	$102.1594	$102.16	$102.15	$102.20
Purchase #7	$218.96	12.162%	$245.5899	$245.59	$245.60	$245.60
7 purchase totals =	$735.22		$787.9404	$787.95	$787.95	$788.10