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	$94.45	10.870%	$104.7167	$104.72	$104.70	$104.70
Purchase #2	$249.90	8.731%	$271.7188	$271.72	$271.70	$271.70
Purchase #3	$125.76	11.364%	$140.0514	$140.05	$140.05	$140.10
Purchase #4	$91.96	9.289%	$100.5022	$100.50	$100.50	$100.50
Purchase #5	$29.93	8.135%	$32.3648	$32.36	$32.35	$32.40
Purchase #6	$33.48	5.809%	$35.4249	$35.42	$35.40	$35.40
Purchase #7	$218.98	13.527%	$248.6014	$248.60	$248.60	$248.60
7 purchase totals =	$844.46		$933.3802	$933.37	$933.30	$933.40