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	$176.87	7.751%	$190.5792	$190.58	$190.60	$190.60
Purchase #2	$241.36	12.393%	$271.2717	$271.27	$271.25	$271.30
Purchase #3	$113.28	13.782%	$128.8922	$128.89	$128.90	$128.90
Purchase #4	$240.69	13.192%	$272.4418	$272.44	$272.45	$272.40
Purchase #5	$96.41	7.175%	$103.3274	$103.33	$103.35	$103.30
Purchase #6	$198.67	13.179%	$224.8527	$224.85	$224.85	$224.90
Purchase #7	$40.43	4.541%	$42.2659	$42.27	$42.25	$42.30
7 purchase totals =	$1,107.71		$1,233.6309	$1,233.63	$1,233.65	$1,233.70