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	$88.92	6.557%	$94.7505	$94.75	$94.75	$94.80
Purchase #2	$29.45	7.421%	$31.6355	$31.64	$31.65	$31.60
Purchase #3	$168.50	10.812%	$186.7182	$186.72	$186.70	$186.70
Purchase #4	$133.28	6.185%	$141.5234	$141.52	$141.50	$141.50
Purchase #5	$103.45	4.453%	$108.0566	$108.06	$108.05	$108.10
Purchase #6	$204.42	12.257%	$229.4758	$229.48	$229.50	$229.50
Purchase #7	$100.35	8.167%	$108.5456	$108.55	$108.55	$108.50
7 purchase totals =	$828.37		$900.7056	$900.72	$900.70	$900.70