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	$134.81	5.396%	$142.0843	$142.08	$142.10	$142.10
Purchase #2	$87.92	5.578%	$92.8242	$92.82	$92.80	$92.80
Purchase #3	$83.70	8.511%	$90.8237	$90.82	$90.80	$90.80
Purchase #4	$139.59	10.512%	$154.2637	$154.26	$154.25	$154.30
Purchase #5	$56.51	12.841%	$63.7664	$63.77	$63.75	$63.80
Purchase #6	$82.43	4.802%	$86.3883	$86.39	$86.40	$86.40
Purchase #7	$160.49	9.317%	$175.4429	$175.44	$175.45	$175.40
7 purchase totals =	$745.45		$805.5935	$805.58	$805.55	$805.60