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	$186.78	5.127%	$196.3562	$196.36	$196.35	$196.40
Purchase #2	$191.84	13.434%	$217.6118	$217.61	$217.60	$217.60
Purchase #3	$221.32	5.415%	$233.3045	$233.30	$233.30	$233.30
Purchase #4	$54.28	9.769%	$59.5826	$59.58	$59.60	$59.60
Purchase #5	$43.39	12.779%	$48.9348	$48.93	$48.95	$48.90
Purchase #6	$157.54	11.231%	$175.2333	$175.23	$175.25	$175.20
Purchase #7	$246.43	6.128%	$261.5312	$261.53	$261.55	$261.50
7 purchase totals =	$1,101.58		$1,192.5544	$1,192.54	$1,192.60	$1,192.50