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	$174.62	12.553%	$196.54	$196.54	$196.55	$196.50
Purchase #2	$166.70	9.121%	$181.9047	$181.90	$181.90	$181.90
Purchase #3	$160.76	8.325%	$174.1433	$174.14	$174.15	$174.10
Purchase #4	$41.39	10.545%	$45.7546	$45.75	$45.75	$45.80
Purchase #5	$163.85	6.753%	$174.9148	$174.91	$174.90	$174.90
Purchase #6	$28.26	5.274%	$29.7504	$29.75	$29.75	$29.80
Purchase #7	$248.47	11.816%	$277.8292	$277.83	$277.85	$277.80
7 purchase totals =	$984.05		$1,080.8370	$1,080.82	$1,080.85	$1,080.80