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	$103.31	7.664%	$111.2277	$111.23	$111.25	$111.20
Purchase #2	$223.28	4.449%	$233.2137	$233.21	$233.20	$233.20
Purchase #3	$76.58	8.177%	$82.8419	$82.84	$82.85	$82.80
Purchase #4	$6.77	8.501%	$7.3455	$7.35	$7.35	$7.30
Purchase #5	$47.41	7.174%	$50.8112	$50.81	$50.80	$50.80
Purchase #6	$163.30	10.367%	$180.2293	$180.23	$180.25	$180.20
Purchase #7	$240.51	12.490%	$270.5497	$270.55	$270.55	$270.50
7 purchase totals =	$861.16		$936.2190	$936.22	$936.25	$936.00