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	$30.63	3.672%	$31.7547	$31.75	$31.75	$31.80
Purchase #2	$213.76	8.248%	$231.3909	$231.39	$231.40	$231.40
Purchase #3	$92.89	6.119%	$98.5739	$98.57	$98.55	$98.60
Purchase #4	$101.41	3.829%	$105.293	$105.29	$105.30	$105.30
Purchase #5	$92.67	11.234%	$103.0805	$103.08	$103.10	$103.10
Purchase #6	$113.61	3.736%	$117.8545	$117.85	$117.85	$117.90
Purchase #7	$231.93	13.791%	$263.9155	$263.92	$263.90	$263.90
7 purchase totals =	$876.90		$951.8630	$951.85	$951.85	$952.00