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	$209.55	10.867%	$232.3218	$232.32	$232.30	$232.30
Purchase #2	$85.39	5.207%	$89.8363	$89.84	$89.85	$89.80
Purchase #3	$240.33	4.689%	$251.5991	$251.60	$251.60	$251.60
Purchase #4	$10.94	12.373%	$12.2936	$12.29	$12.30	$12.30
Purchase #5	$211.75	12.679%	$238.5978	$238.60	$238.60	$238.60
Purchase #6	$186.92	7.276%	$200.5203	$200.52	$200.50	$200.50
Purchase #7	$46.61	5.640%	$49.2388	$49.24	$49.25	$49.20
7 purchase totals =	$991.49		$1,074.4077	$1,074.41	$1,074.40	$1,074.30