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	$29.94	4.697%	$31.3463	$31.35	$31.35	$31.30
Purchase #2	$17.36	11.323%	$19.3257	$19.33	$19.35	$19.30
Purchase #3	$98.63	4.646%	$103.2123	$103.21	$103.20	$103.20
Purchase #4	$100.77	11.500%	$112.3586	$112.36	$112.35	$112.40
Purchase #5	$141.94	7.143%	$152.0788	$152.08	$152.10	$152.10
Purchase #6	$191.36	11.563%	$213.487	$213.49	$213.50	$213.50
Purchase #7	$89.39	12.404%	$100.4779	$100.48	$100.50	$100.50
7 purchase totals =	$669.39		$732.2866	$732.30	$732.35	$732.30