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	$189.64	3.613%	$196.4917	$196.49	$196.50	$196.50
Purchase #2	$38.69	6.140%	$41.0656	$41.07	$41.05	$41.10
Purchase #3	$181.94	6.199%	$193.2185	$193.22	$193.20	$193.20
Purchase #4	$88.60	12.417%	$99.6015	$99.60	$99.60	$99.60
Purchase #5	$215.30	10.836%	$238.6299	$238.63	$238.65	$238.60
Purchase #6	$28.49	10.107%	$31.3695	$31.37	$31.35	$31.40
Purchase #7	$42.75	9.241%	$46.7005	$46.70	$46.70	$46.70
7 purchase totals =	$785.41		$847.0772	$847.08	$847.05	$847.10