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	$175.90	9.175%	$192.0388	$192.04	$192.05	$192.00
Purchase #2	$173.87	9.543%	$190.4624	$190.46	$190.45	$190.50
Purchase #3	$105.46	6.142%	$111.9374	$111.94	$111.95	$111.90
Purchase #4	$137.30	13.178%	$155.3934	$155.39	$155.40	$155.40
Purchase #5	$7.36	3.761%	$7.6368	$7.64	$7.65	$7.60
Purchase #6	$131.55	13.150%	$148.8488	$148.85	$148.85	$148.80
Purchase #7	$118.49	5.464%	$124.9643	$124.96	$124.95	$125.00
7 purchase totals =	$849.93		$931.2819	$931.28	$931.30	$931.20