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	$104.67	5.574%	$110.5043	$110.50	$110.50	$110.50
Purchase #2	$211.72	13.245%	$239.7623	$239.76	$239.75	$239.80
Purchase #3	$93.37	13.232%	$105.7247	$105.72	$105.70	$105.70
Purchase #4	$184.36	8.613%	$200.2389	$200.24	$200.25	$200.20
Purchase #5	$164.40	10.149%	$181.085	$181.09	$181.10	$181.10
Purchase #6	$216.37	10.116%	$238.258	$238.26	$238.25	$238.30
Purchase #7	$73.27	12.354%	$82.3218	$82.32	$82.30	$82.30
7 purchase totals =	$1,048.16		$1,157.8950	$1,157.89	$1,157.85	$1,157.90