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	$183.81	7.131%	$196.9175	$196.92	$196.90	$196.90
Purchase #2	$69.45	12.255%	$77.9611	$77.96	$77.95	$78.00
Purchase #3	$208.83	3.521%	$216.1829	$216.18	$216.20	$216.20
Purchase #4	$98.55	3.217%	$101.7204	$101.72	$101.70	$101.70
Purchase #5	$124.51	5.653%	$131.5486	$131.55	$131.55	$131.50
Purchase #6	$25.64	9.216%	$28.003	$28.00	$28.00	$28.00
Purchase #7	$138.62	11.600%	$154.6999	$154.70	$154.70	$154.70
7 purchase totals =	$849.41		$907.0334	$907.03	$907.00	$907.00