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	$228.58	5.217%	$240.505	$240.51	$240.50	$240.50
Purchase #2	$7.55	7.484%	$8.115	$8.12	$8.10	$8.10
Purchase #3	$182.55	4.130%	$190.0893	$190.09	$190.10	$190.10
Purchase #4	$152.98	13.522%	$173.666	$173.67	$173.65	$173.70
Purchase #5	$142.69	6.602%	$152.1104	$152.11	$152.10	$152.10
Purchase #6	$79.51	3.646%	$82.4089	$82.41	$82.40	$82.40
Purchase #7	$119.43	6.743%	$127.4832	$127.48	$127.50	$127.50
7 purchase totals =	$913.29		$974.3778	$974.39	$974.35	$974.40