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	$92.97	3.834%	$96.5345	$96.53	$96.55	$96.50
Purchase #2	$70.28	11.137%	$78.1071	$78.11	$78.10	$78.10
Purchase #3	$214.35	4.353%	$223.6807	$223.68	$223.70	$223.70
Purchase #4	$184.80	6.253%	$196.3555	$196.36	$196.35	$196.40
Purchase #5	$6.44	10.234%	$7.0991	$7.10	$7.10	$7.10
Purchase #6	$103.85	10.186%	$114.4282	$114.43	$114.45	$114.40
Purchase #7	$176.60	7.177%	$189.2746	$189.27	$189.25	$189.30
7 purchase totals =	$849.29		$905.4797	$905.48	$905.50	$905.50