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	$158.62	10.627%	$175.4765	$175.48	$175.50	$175.50
Purchase #2	$207.56	7.188%	$222.4794	$222.48	$222.50	$222.50
Purchase #3	$150.95	11.565%	$168.4074	$168.41	$168.40	$168.40
Purchase #4	$115.92	6.185%	$123.0897	$123.09	$123.10	$123.10
Purchase #5	$39.31	3.575%	$40.7153	$40.72	$40.70	$40.70
Purchase #6	$226.31	5.606%	$238.9969	$239.00	$239.00	$239.00
Purchase #7	$76.26	5.434%	$80.404	$80.40	$80.40	$80.40
7 purchase totals =	$974.93		$1,049.5692	$1,049.58	$1,049.60	$1,049.60