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	$173.71	8.139%	$187.8483	$187.85	$187.85	$187.80
Purchase #2	$177.78	11.287%	$197.846	$197.85	$197.85	$197.80
Purchase #3	$246.90	7.161%	$264.5805	$264.58	$264.60	$264.60
Purchase #4	$70.85	10.595%	$78.3566	$78.36	$78.35	$78.40
Purchase #5	$168.73	8.448%	$182.9843	$182.98	$183.00	$183.00
Purchase #6	$68.58	4.536%	$71.6908	$71.69	$71.70	$71.70
Purchase #7	$202.65	5.118%	$213.0216	$213.02	$213.00	$213.00
7 purchase totals =	$1,109.20		$1,196.3281	$1,196.33	$1,196.35	$1,196.30